I had guys who,when we started dating, claimed that they wanted a relationship, the same things I did. Then after a while, I find out, nope, they were just after fun.
I told myself it's cause I wasn't hot enough/110lbs and thats why they didnt continue into a relationship with me...so you know what, at the end of the day, it does come down to how you see yourself.
We all love attention from the opposite sex, that those we find attractive find us attractive back.
The scenario you described, I can see two ways of looking at it...
1) confident woman: wow, this attractive guy could of had his pick of hot woman to chase but he finds me physically attractive that he needed to reach out to me - I wonder if he does this to women he finds attractive on a regular basis.(which btw, could be all he want/can handle in his life right now)
2) not confident woman: why did he not ask me out on a proper date? Why is he only wanting sex from me? Is it cause I'm not at my goal weight? Would he have acted in the same manner if I was skinnier/taller/hotter/better.....
I've been mostly leaning towards the second version myself when something doesn't work out with a guy I like...but then again, if the guy only treats me properly when I look perfect, that kind of superficial guy is scary and not the kind of guy I would want long term in my life anyway...
But when I'm right in it, I can't see that...
I'm a work in progress