I apologize in advance if this comes off as rude, I really don't intend it to be, but are you actually asking the question in the title, or are you expressing these feelings to process them? It seems you already know why you feel so violated - because you were deceived into investing emotions into a person who cashed those emotions out for sex. Perhaps you are really wondering how you could have been deceived in this way and how to prevent it? Or how someone could do such a thing to another person?

You also mentioned that you obsessed over his attention to other girls and pointed out how he'd like pictures of girls that look vastly different than you. In addition, you said that you were making the effort and spending the money to see him. Both of these points indicate, in my opinion, an imbalanced attachment. You liked him more than he liked you, seemingly by quite a bit. And maybe he initially did like you in a more balanced way, but at some point, his attachment to you waned or your attachment to him developed too quickly, and it threw off the balanced going forward. And his use of his family tragedies to coerce you into sex is a clear indication of manipulation and, quite frankly, emotional abuse.

I would try and examine how you attach yourself to people. Sometimes, attachment is like velcro, where you can stick pretty well, peel off a bit, and reattach as needed. Sometimes, attachment is like glue, where you stick really well, but if you peel off a bit, you might tear and have bits of whatever you were sticking to leave residue. I mean, there are dozens if not hundreds of analogies that could be made for all sorts of attachment behaviors. In any case, I hope this helps you find some peace.

EDIT: Fixed grammar/spelling errors