DAE feel like an ass when they ask someone to repay them on a loan or for bills?

I hate the feeling of asking someone to pay me back, even though they should realistically be the one that feels like the asshole. I am a nice guy, and I have loaned money to my roommates who struggle a bit more to pay bills than I do. I even let it slide when they needlessly spend their money on things, rather than paying me back right away. Even after all of this, I still ALWAYS get the feeling that I am in the wrong in the situation, and I don't know why. Agree?