What am i so afraid of?

Basically i'm extremely insecure. I think it's mostly to do with the way my body looks even though (if i do say so myself) i have a nice slim figure and (again, sorry for the big-headedness) i'm quite pretty. Recently ive met a guy who's very good-looking and obviously a bit of a ladies man, but he quite clearly is attracted to 'fit' girls with fab bodies and are just generally very sexy and hot, and it's like even though i know he's attracted to me, i feel like i just can't compete with that. I've no idea how i've got myself into this state of mind but i'm literally sat in tears because i feel so crap. It's pathetic i realise, but i feel as though the only way i'll be happy is if i miraculously physically changed overnight into some kind of Goddess. I feel like giving up before i've started. We're meant to be meeting up again in a few weeks, but i feel like just not bothering. I don't want to be compared to anyone, and i just know how distraught i'll feel if he changes his mind about me. Before anyone comments, i have no time or money for 'therapy', i'm 19 and a student.