s_l: I've had a similar set of circumstances, and have had to overcome similar challenges over the years. In my case, I was isolated by my peers at a young age, and retreated into solo pursuits like you have. I've also missed out on a lot of social experiences, and am in the process of learning social protocols, at 30, that most people seem to learn in jr. high or high school.
In my experience, medication is not useful in the long term. In the short term, it can provide relief of symptoms, but generally don't treat the underlying cause. Over time, tolerance develops, symptoms worsen, and the side effects begin outweighing the utility of the medication. Also, in many/most cases there is the issue of addiction to deal with, which makes things a whole lot worse. My experience (with pharmaceuticals at least) are limited to benzos and SSRIs.
What works for me? Exercise, therapy, and over time a slowly increasing frequency of socialization. I'm an introvert as well, so in-person socialization can be exhausting, but it is very rewarding from a mood elevation standpoint, and really helps with social confidence-- which, I don't have to tell you, is critical.
The most important thing, for me at least, was seeing a psychologist. It was a catalyst for a huge change, and was able to treat the underlying cause of the problem rather than the surface symptoms. Even just having a neutral, sympathetic ear to talk to can help heaps.
In the end, if you're looking for a quick fix for a few months to a year or two, then meds are fine. If you're looking to fix the problem, and are willing to put a fair bit of effort into doing so, then therapy is the real solution. It's a lot harder than popping a pill, but the absence of side effects and duration of relief are well worth it.
Best of luck!