It happens, just try to shrug it off and don't engage with him anymore.
I'm luckily very good at separating emotion from sex, perhaps even to my detriment. Certainly let a client treat you, gift you things, but always remember that at the end of the day it is a financial relationship. Don't listen to anything else they spout. I've been told by more than a few clients that they are in love with me, I just remind them of what the relationship is. And when I've gotten sweet on a client, I've told them I can't see them anymore. Try to be brutal, hard as it may be, otherwise you run the risk of being emotionally battered black and blue.