fear and insecurity

It all feels a bit heavy. I mean in a literal sense it is; I feel that my thighs belong to a 200 pound man, that my stomach belongs to a 180 pound man my muscles belong to a 100 pound boy; its all very disproportionate. the sense of shame and guilt does not let me be happy, and now i am scared that in my next trip to the beach i wont be able to function and my lame excuse that i hate sea animals will once again keep me from enjoying life. I should do something about it, you say. well i think so too, the problem is that in the middle of all my stress, my depression, and my sense of inferiority I am not even able to get up from my lazy butt and exercise. the feeling that people watch, or critique follows me everywhere it haunts every single moment of the day. In reality all i need is a bit of toning, and it all scares me because i do not see it that way. I feel that i should loose at least 15- 20 pounds that i should stop eating all together. If i were comfortable throwing up i would, thankfully I am not; and if I stop eating I get the worst headache in the world and I am not able to function normally during the day. What should I do with my insecurities and my fears?