why?

Today I got pills. Pills that I felt for the longest time would be the answer, but I know they are not. I feel so many things that I don't think anyone else does. I don't think anyone will ever understand. I feel so trapped in the constraints of time, of humanity, of this world. I feel like I can't just live my life without worrying. I wished for the longest time that I had a boyfriend. Now I do, and I feel like my friendships are slipping away. Why can't I just be happy? I feel like there is no solution. I hate walking around places alone, going grocery shopping alone. But at the same time, sometimes I hate being with people. Sometimes people annoy me and I want to be away from them. Why can't I just be satisfied? I get high marks and I'm still not satisfied. Why? What's wrong with me? I have everything I could possibly want but I still feel sad all the time! It's not even that I'm anxious about school or about the future- it's just that I'm constantly sad. I try to help others, yet inside, I still don't feel fulfilled, I still don't feel like I'm worthwhile. I feel like I'm useless a lot of the time- sometimes I just want to jump in front of a train. I've thought about just running away, leaving everything in life behind me and just ending my life. I don't know what I'm living for and what the point of everything is! I'm so confused about everything. I feel like I'm too old for university but too young for the "real" world. I just want to be able to chill out, to relax, to enjoy. Why can't I?