Just like men, women like a challenge. We tend to think that we can make that man who has other women choose us over them. But honestly, why would he choose when he is getting what he wants out of the situation? Yeah, he likes you. You get some great conversation, great intimacy and some gifts along the way. Unfortunately, that's where it ends. Very seldom does this "homie lover friend" become your life partner or husband.
If you are honest with yourself in the beginning, it will always be what it is. Even if you catch feelings, there is very little chance that the two of you will become an item. Especially if you expect him to be exclusive. He has shared all of his other relationships with you and you happily accepted them. So think really hard on why he would wait until now to change. And in most cases, when you express to him that you want to be exclusive, he is gonna agree to work at it. He is gonna say whatever you want to hear. He doesn't want to lose any of his options, so the goal is to appease you by saying anything to please you at that moment.
Don't be upset with yourself when have that aha moment. It happens to the best of us. After all, who doesn't want exclusivity? Most women don't want to share, but we tend to settle and dream up all the possibilities in our heads. Pick yourself up. Stop accepting his calls, stop letting him stop by. Don't make excuses for anything and move on.
Instead of dwelling on how hard you fell for him, turn that energy into something positive and productive. Work on you. Try and figure out how you won't get into a similar situation in the future. Spend some time with your child. Find a new hobby if that helps. But don't spend anymore time worrying about a man who isn't worried about YOU!