How to build up my self-esteem?

So I've been overweight since I was like 6. I'm now 15 and I'm not incredibly big, I got tall (like 5'10) but I still have big thighs, arms and stomach. I'm working on losing it. I'm about 30 or so pounds over. I've always been teased about it and called names. Once I started high school people didn't say anything much and I developed a pretty good personality. My boyfriend of 9 months calls me cute, pretty, beautiful and gorgeous. I don't believe him but I don't want to be one of those annoying, whiney girlfriends so I just return the compliment. No body knows, but I was bulimic for almost a year and recently got over it. I've had two big tragedies happen (one affected the whole family, one only me) in the same year and food's been my comfort. I know that's not good. Especially when trying to lose weight. And what doesn't help is that my boyfriend is skinnier than me... He weighs 130 pounds, he's lanky (He's underweight and 6'0 but I still feel like I should be smaller than him). I can look in the mirror and think "Hey... I look okay today." but then I see myself next to him and feel like a whale. I could never leave him over this, I love him so much. Just being around him and seeing his body compared to mine makes me feel like crap. And my height's always been a problem with me. I hate being this tall. Then I see the perfect girls at my school, they're 5'6 or 5'7 and weigh like 110 or 120 pounds. I wish I could be like them. I just feel so ugly, fat and down about myself. Also I took a picture of myself on my webcam with my shirt up (breasts covered) of my stomach for motivation to lose weight. Like I'd look at it and remember how happy I'd be to get rid of it and I think my boyfriend saw it and now I feel so gross. I can only imagine what he thinks. He kept asking why I hid my screen so fast when I pulled up my pictures (I forgot about it) and I told him it was none of his business. He said he thinks he saw a picture but he's not sure what it was. I'm pretty sure he knows that it was me with my shirt up. I'm worried that he thinks I'm sending shirtless pictures to people online or something... But I deleted it and he's dropped the subject since I was uncomfortable with it. I feel embarrassed to tell anyone I'm trying to lose weight. How can I raise my self-esteem so that I don't feel so horrible every day? Thanks.. :)