Hi! I can see how you would feel this way, given that you were burned in that other relationship. Since it is taking such a toll, I suggest you see a therapist to work through it.
That said, alas, people have gotten to the point where they expect sex while dating. I agree that if you don't feel a sense of love toward the other person, then sex is just two bodies rubbing together, with all the possible negative results. And if you don't enjoy that, then why do it?
While you heal, you can take a break from dating. Let's hope at some point you will meet a guy who is willing to hold off on the sex until you feel ready, even if that is after marriage. These guys are out there!