I like what Znegative, says bro. Listen to him. Stop while you're ahead with the opiates especially. Only you can decide if you're a drug addict, but there are definite signs in what you're stating. All those drugs in a short period of time at a young age, will likely form you into a person with hard drug addiction that you will battle for the rest of your life. I mean there isn't anything wrong with experimenting, but like stated above you are definitely playing with fire. Stick to the weed, maybe a little drinking, cuz I know you are going to keep using whatever regardless of the warnings we give you.
Playing with the hard drugs like opiates, especially heroin, like Znegative said, there will be boundaries you swore you wouldn't cross that you will find yourself crossing. Like swearing you won't shoot up, or stealing from friends/family. It's reality bro, and I was one of those people who swore I wouldn't do those things. I started at 14 with weed and alcohol. I'm 32 now, basically homeless, been to prison 3 times, and countless jail visits. I've thrown my life away man. You have a lot of potential to be successful bro, don't jeopardize it man.
Like I said experimenting is whatever, but it sounds like you are looking for that perfect drug to make you the happiest, and thus likely that will result in addiction. And by the way you talked about the opiates, it sounds like this is the one you should avoid most, because you liked it so much. And opiate addiction is no fun. Let me tell you dude. Znegative put it right, it will literally become your life, everything and all your time will revolve around it. And if you are afraid of withdrawal dude, this is the biggest and baddest monster you will ever see.
Quit while you are ahead, and like I said, if you want to keep using, stick to the cannabis. It sounds like your cup of tea, and it isn't likely to destroy your life and opportunities. Hope you listen to all these people here man. We have been through it. I'm glad you asked us about it.