I've had a really messed up year

I've had a really messed up year. I've never been a very confident person consistently. Ever since I was a little girl, I've had very low self esteem, possibly from my dad leaving me at an early age...from my mom's emotional abuse growing up...it doesn't really matter why. But although I've been able to hide my constant insecurity from the rest of the world, and even from myself during certain streches of time, undernearth the happy facade, and the short periods of confidence and clarity, I'm insecure, and always have been. I'm a good student, I have good friends, I try to participate, get invovled, etc, but when my best friend is mad at me, or when a boy doesn't like me, I can't pull myself together, and it's really starting to effect my life. My year of problems have stemmed from this one guy...call him daniel, who I broke up with last summer when he left for six weeks. I liked him a lot, but didn't like him enough to stay with him for his time away. When he came back, we started hanging out a lot again, but he was really bitter about the break up, and he wasn't treating me well. I started to really like him, (not because he wasn't treating me properly) but because he's funny, kind, sweet etc... atleast when he's not angry abotu soemthing. I was really insecure and shy around him, because he wasn't showing me the attention he had previously showed me. He would tell me he wanted to be with me, and then do something completely different. There was another girl he was trying to get with, and he was constantly flip flopping between us, and other people, which brought my feelings of inadequacy to the surface, and I became bulemic because I didn't think I was thin enough, (this girl was thin) and I thought I wasn't pretty enough so I became very self concious over my appearance, and as well as my actions. I became somewhat obssesed with other girls that he was interested in, and feel guilty that I wasn't smart, pretty, funny, or interesting as them. I also slept with two guys that I didn't like, and whom I knew only liked me because they thought I was good looking.

After a while, daniel forgave me for breaking up with him "breaking his heart" that summer, and we were together...not officially, but together. He cheated on me with two different girls, and slept with me after he hooked up with one girl the same night. I had no idea. I'm really bad at getting mad at people, and I'm also really good at understanding, and for some strange reason, I didn't think it was that big of a deal. He's really good with words, and he made me beleive that he loved me and that things woudl be different. So now we're officially dating, which I've wanted for so long, and he's funny, and sweet and kind to me. But I didn't want it to happen this way. Sometimes, I feel as thoguh he's spoiled it for me. Because I think about the past. He's like...a peice of chocolate cake that you've wanted for a really really long time, becuase you love chocolate cake so much, and you were deprived of it as a child, and as an adult, you're offered chocolate cake, and you eat it because you've wanted it forever, you've been obssesed with it and this is your only opportunity, but then you realize it's a little bit stale, but it still tastes good, but not as good as you thought, and you're also afraid it'll make you gain weight, so maybe its not worth it. I'm too afraid to let him go, because I don't know what I would do if he was with someone else. And I don't think I could find anyone as funny sweet smart and cute as he is. I have a lot of boy problems. My best friend says that if I had any respect for myself, I wouldn't be with him now. So my question...welll, how do I stop feeling like I have to throw up when things don't go right? How can I be happy even if my best friend is mad at me, or I'm no longer with my boyfriend? How do I get self confidence if I feel, secretly, as though I wasn't ever born with any? How can I stop caring what other people think so much? How can I stop second guessing everything I do? LIke right now, I'm thinking, about what if people respond and tell me I' m a complete looser. And I'm worried that online strangers will tell me I'm a complete looser, when I don't even know them!