**** you're 14?
Wait for about 7 years, and if you're still feeling the same way, have this crisis then. If I was involved in this stuff when I was 14, I know I'd be in a better situation than I am now.
(oh, and i'd wait till you're about 16 to start tryin drugs)
I'm having a massive crisis NOW because habits that could have been easily corrected when I was 14 weren't, now I'm 19 and I'm trying to dig my way out. Turambar I don't mean to go after you, but a lot of people said the same thing to me and it turned out the worst advice I've ever gotten

About feeling different than everyone else. Kinda a useless answer: but it's either true or it's not

It's a common part of human perception to think that way starting around you age for the next 6-8 years, but it also doesn't always have to be wrong. My mom describes both me and my father as being "born old." It's not entirely consistent, but at a very early age we showed a level of maturity in many manners that would always remain far ahead of anyone else at that age. This sounds great on paper, but it also means we very often didn't find the same things funny or acceptable as the people at that age. And of course the more people grow up often changes what the way they think about relationships and what they expect from them.
Not to be elitist, but it's all expected as soon as you give the hint that you're more intelligent than average that you feel different from others, because you probably are

Thinking more about things tends to come with the territory, and when you think more about things, you learn and mature more. I don't recommend the drugs (that's more of my personal preference on avoiding anything potentially risky that I don't have any real need to do in the first place), and be careful about the ADD thing, it gets misdiagnosed ADD all the time. I'd say if you really try to pour all your will and effort towards focusing on something and it still goes bad, it's time to talk to a psychiatrist and see what he thinks. What most people don't realize is a lot of times it's not the problem of not being *able* to focus, it's just not wanting too. If your motivation to do something isn't strong enough, you won't get anywhere, that's the general rule for anything.
I can't wait for the time when your knowledge will be important more so than the PE lessons...
Everything's important, potentially. Basically everytime you encounter something that wasn't thought of or created by you, you can learn from it

PE often gets screwed up, but the point of it is not only to get you some exercise but try and teach you some ways you can go about it outside of school. Exercise is good, I'm injured currently which made me stop my daily exercises, and it's only now hitting me how much keeping to that daily routine helped my focus, and discipline, not to mention my psychical health in general.
I know I don't post much, but I am usually lurking around and I live for these kinds of topics (I don't get all that much interaction with people myself, so I counterbalance it by absorbing as much information about how people think as I can. These kind of posts are always a goldmine for that ^_^ ). So talk here, send me a PM, whatever of your choosing. Don't be shy, keep talking until you get things worked out