Dear OP,
Draigan gave you some excellent advice.
It's not only possible to be happy and be a loner-in my opinion, it's good, It shows that your a complete person and when you do choose to spend time with others it's because you want to and you enjoy their company, not because you can't handle being alone or dealing with your own thoughts.
However Draigan has pointed out something that should never be overlooked-the need for at least a couple of other people in our lives. This is almost as important as food and water. Humans need other humans. We need them for social reasons (we're social animals and our mental health will suffer if we have no one in our lives) and we need them for physical reasons.
I'm not sure if you know or not but newborn babies can be fed laying in a crib, from a bottle and not being held/cuddled and can have their diapers changed without the person doing it giving them eye contact and without interacting with them. In this way they can be perfectly healthy physically BUT they will actually DIE if this goes on too long. That's how much humans need other humans.
We're also just not designed physically to make it through life without others. We see this on many physical levels-one example being that women have an extremely hard time giving birth alone. Our bodies were designed in a way that assumes another person will be present to help bring us into the world.
So there are a couple of examples to show, in a very practical way, that we do in fact need one another.
Some people happen to need other people more than others. You may be someone who can fulfill your need for others easily through internet friends or other less invasive ways. But I hope you will consider Draigan's advice and be sure that you have one or two constant people in your life that love you unconditionally and that know your story. Try to stay in touch with them-keep each other updated on the in's and out's of each others lives. I think you can still qualify as a loner if you spend only 4 or 5 hours a week-or a half hour a day talking on the phone or having a regular coffee meeting with your best friend.
My partner was a serious loner for about a year and a half-well before I knew him. He's told me stories about it and it doesn't sound pleasant. I became a loner after my 2nd child was born. Even though I was physically around other people-I retreated into myself and was essentially alone in many ways that matter. It made my issues far worse and created a few issues of it's own.
Once I was ready to start coming out of my self made prison-it took me a while to re-learn how to interact with people. I scared a few people off because I no longer was in practice of social skills. Fortunately, I also had a loving partner who would point out things I was doing that scared people away. He did so in a loving way although it was still hard to hear at first. In the end, he helped me so much and I was able to re-connect with some close friends and make a couple new ones.
I'm a fairly social person ordinarily--for whatever reason I was going through a period of isolation. Everyone is unique in their need of others and I think it helps if your aware of what your own unique needs are. For example, the way I see myself is that I like having numerous 'buddies' that I can hang out with, bump into when I'm out and join at their table in a restaurant. I like these people but I wouldn't keep in touch with them if I moved away. Then, I have a couple of true friends. These people are like family to me and I treat my relationships with them with the same care and value that I do my relationship with my partner and my close family. I really invest a lot in my two closest friends. I would do anything for them--and they know how much they mean to me and that they can count on me. They reciprocate this and I know I can count on them. They know everything about me--
One thing that I require in the job description of best friend is unconditional love. That doesn't mean we should enable poor habits or behavior in each other. It means that even if we're a fuck up-we know they will still love us. This means that I feel safe telling them anything because I know they will still love me. I also expect them to be honest with me. To tell me if they think something I am doing is not the best choice I could be making, tell me if I am acting like a jerk--but even if I choose to continue making poor choices or being a jerk--they will still love me and still be there for me. (A side note, this does not mean that they have to harm themselves to support me though--I don't ever expect them to give me their last dollar so I can use it to make a poor choice)
And, I do the same for them. I feel safe telling them when I think they are F ing up--because I know I can be honest with them and they will still love me.
So-This is how I see my own need for others, a couple close friends who I share unconditional love with and a large social network of people to hang out with, talk with, share ideas with and just goof off and play with.
I think it's good if we all are aware of our unique need for others. Maybe you don't need much at all from other people, maybe your a loner 99.9% of the time BUT it is very, very important that you have someone in your life that you are close with.
And I realize you may be having a hard time with people right now but I think it's almost impossible to not ever let anyone in again. It's against human nature. We ALL feel burned the way you do right now--at some point, we all feel that way. We just learn to be more cautious with who we "let inside" and learn that our friendship and love is valuable and treat it as such.
I hope that you will find a way to be close with at least one person. Sometimes it can be good to look outside of your peer group. (especially now days the way our culture is). My best friend is a conservative 60 year old man. However, he loves me and accepts me for who I am. He doesn't judge me. I can tell him anything. We don't go out to dance all night at raves together--he isn't a part of my peer group at all, none of my 'social' friends know him. But we hang out and drink wine and play music together, we watch movies together, I help him work, we cook meals together. We just adore each other and have found some common ground that we enjoy together. In fact, I think it's better that we're nothing alike! Why does it matter so long as we love each other unconditionally?
You may find that looking 'outside the box' so to speak, right now, is your best place to start to rebuild your trust in others. Is there an old family friend? Am aunt or uncle you trust that won't tell all your secrets?
Anyway, I'm rambling now--I hope this helps you. We are all disappointed in humanity at times but you can't go grouping ALL human beings in the same category. That would be prejudiced. Give people a chance to show you who they are as unique (and always imperfect) human beings. I'm 100% positive that there is at least one person in the universe that you can connect with.
Blessings