I have the same problem. Even if you get out alone, you should make a point to get out. My town isn't huge, so I struggle with finding friends, too, but look online for meetup groups or people with similar interests. You have internet, put it to good use! I got involved with a group of people that share my faith and I never even thought they existed in my town, it seemed like everyone here were Christians of some sort (which is fine with me, but they aren't as understanding toward my faith, usually).
Do you like to exercise or do physical activity? Check out Craigslist or somewhere similar for a workout buddy. Online personal ads usually have a "platonic" section for people just looking for friends. Those can be places to look for people in the same situation. There's plenty of people you can talk to online first before meeting if you have some kind of anxiety problem keeping you from getting out more. Introducing yourself to the neighbors is also a good step, but I noticed living up in Northern USA people don't do that much, so maybe that's just the Southerner in me speaking.
I'm not sure of your location.
As for using, I second what others said, that you should keep your drug use to yourself until you are good friends with a person and either know for a FACT that they are 100% okay with it or that they also use. Small towns are the worst, that was one reason I left the town I ended up coming back to. Make a couple of innocent mistakes and everyone will know. Just be careful about who you trust, but do give yourself the chance to find to some new people to interact with. Sitting alone at home just leads to being depressed and using more because you're sad and lonely all the time and want something to fill that hole. Something I'm very familiar with. I had to almost force myself to meet new people, but it led to much better things for me and I feel much better for doing so.
