Just being a teen

I'm confused. I really am. Sometimes I feel like I'm on the right track in life and that everything is going smoothly, and then other times I feel like my whole world is crumbling and i am only left with the shattered pieces of my life.
Some people think I am depressed, some think I have low self-esteem , but I want to believe that I'm only trying to find myself in this relatively large planet. Take for example, right now in my life I feel like I need a boyfriend. I just feel like a boyfriend will solve at least quarter of my problems; problems that are yet to be defined. But the reasonable, logical and analytical part of me is totally against it. That part of me has given me several reasons as to why a boyfriend is a totally bad idea; He will distract me from my studies (if you haven't figured, I'm a nerd).
He will demand physical contact that I am not ready for.
He will realize how blind he was to ask me out and eventually break up with me.
The break up will lead to my being depressed and viewing all guys as jerks.
Then I will end up as a single old lady living with fifteen cats (cliche, I know).
So I have come to live with the fact that I am better off as a friends to guys.
Since we are talking about guys and my status with them, I'll let you in on my first experience with a crush as a teenager. So I liked this guy and I considered him as my best friend. I told him everything (well everything except my feelings for him),and he also shared everything with me. We were always together and spent most times teasing each other. He would tell me about his troubles with his girlfriend and as a good friend that I was, I would listen and give him advice on how to handle the matter. Well fortunately for me, he eventually broke up with her.
One day he asked me out, that was several weeks after the break up. I didn't say yes right away but eventually I did. He would hug me and look at me like I was the only one worth looking at. I was in cloud nine. Anyways, the problem started when he was kissing me and attempted to reach base three with me. I resisted and I guess that was when he realized I wasn't relationship material. I figured that instead of him breaking up with me, I should do it instead. So I broke up with him and that was the end of our relationship/friendship.
After him I lost hope of being suitable girlfriend material. I realized that I am destined to be just a friend to guys. So that is a summary of my love life.
Then there is my education. The subjects I'm expected to be good at are the thorns in my flesh. Maybe the reason I don't make distinctions in chemistry is because there is no chemistry in my life. Well, at least my mathematics is amazing.
Anyways, back to the relationship section. With my friends, I feel like the DUFF(Designated Ugly Fat Friend), or in my case DUTF(Designated Ugly Thin Friend). I don't know why they are friends with me, but they are. Silly right? At least they are sane enough to only see me as a friend. I wake up everyday feeling like I am the shadow of my friends. Don't get me wrong, I love them but I feel like they constantly outshine me. Maybe they don't see it the way I do but that's just how I feel.