boyfriend issues

so my boyfriend and I've been with each other a little over two years. I promised myself to the lord and he doesn't seem to grasp that concept.. he constantly asks and asks and it makes me look like the bad guy everytime I say no..
like I guess it what keeps the relationship alive.. but all I want is the assurance that I'm loved, not just a piece of ass. 
so in short, I still want to be with him..but I don't know how to stop this "lets have premarital sex" thing.