How can i get my Boyfriend to understand?

I hate my body, my tummy and thighs are too big for me. My boyfriend thinks i'm beautiful. But i really dont think i'm beautiful. My tummy is too chubby, and my thighs are massive,. I call them my thunder thighs. my boyfriend always say i am always down on myself. I am, but this summer i started working out some, to tone up. I am 17 5 ft 5, and 150 lbs. I really dont like my body at all. I am working on just toning up, not necessarily loosing weight. I want to be fit. My BF is very Sporty. i am not. Not at all. i suck at sports. But i want to be fit now, and i want to do a sport in my senior year of high school. Last night my BF and i had an argument because i hate my body. He pushed me to the point of tears. I was so upset with what he was saying to me. And it hurt. I really just want to be Toned and IN SHAPE and FIT!!! but my BF thinks i hardly eat, and i workout too much. BUT i eat a lot, and i work it off. i take plenty of breaks, and i really dont over work myself. I dont know how to make him understand that i'm not going into the danger zone of anything. And that he wont lose me. he has protectiveness issues,and maybe he thinks that if i get fit, more guys will look at me. but i want to get fit for me!! no one else.. JUST ME!! will someone please give me advice on what i should say or do. I've told him how i feel, and he just thinks i keep bringing my self down. He is very fit and tiny, so i dont think he truly understands what a teenage girl goes through. Please help me!!