Okay, now, I'm not the kind of person that is going to say someone can't prefer to date someone with a certain body type.

But this...

>if I don’t lose weight he’s going to leave me like he did his previous two girlfriends (both for being overweight).

Sounds like a recurring theme that probably stems from him being hypercritical. And this...

>“I don’t want to be hanging around with my friends and thinking that THEY could be thinking I could do better than you”.

Just... What? How old is he? You say 27, but I don't think he's progressed mentally from 12.

Add all that on top of the fact that you were in an accident, you are working on it, you aren't much bigger than when you met and he's even more concerned with the actual number than what you look like or whether you're healthy.

So, what would he be like if you get down to what he deems "acceptable" and then you two have a baby? Be telling you that you aren't losing the baby weight fast enough and what will his friends think while you have an infant hanging off your boob, while washing up puked on clothes and with a pile of crappy diapers to take out?

Yeck.