yes, I is of the male persuasion!!
I must say that when I paid my ex compliments after she gave birth, I got an earful, so I did stop for a while until her complaints about me not saying how beautiful she looked etc got too much but then as she thought she was ugly I was only saying so as a platitude couldn't win
now my ex did have a gorgeous arse bum, there was something that drew me to it all the time even when it grew twice as big after birth, but as she thought it was hideous, I was 'told off' as I could only possibly be making fun of her and as for touching, holding, squeezing, fondling said body part, well if something sharp was handy I wouldn't have a hand left.
we males do get confused by you females.
we have to find the fine line between what you mean and what you want if that makes sense? if you say, tell us, believe yourself often enough that you think you are horrible, most women I know are very convincing and all of a sudden you don't know whether to agree to make you happy or disagree to make you happy.
to your question about why he is with you. most of my ex g'f's were curvy including my sons mum, my g'f now (if she comes back to england possibly ) is very slim, ( I did make the mistake of saying I could feel her hip bone in my stomach one day but thankfully it was before she had the level of good english she has now [phew] ) some were blond, some brunette, some tall, one very short ( I am quite tall apparently), but the thing they all had in common was great personalities.
your ex is with your because thats where he wants to be, with the woman he met and fell for, you are still that same person but without the confidence of belief in yourself. take your time, go out together, have faith (oh and maybe give him a good hint as to what you really want him to say, go on give him a good clue???