I've been with my boyfriend for 9 months and I love him to pieces. We have a great relationship and our sex life, i find, is very normal for a couple our age.

I enjoy doing sexual things with him, but every now and then afterwards I will feel really strange. I feel like I regret it or something, even though I don't, and I start to feel rotten about myself and want to curl up and cry. I don't understand why I sometimes feel this way because, like I said, I enjoy doing sexual things with him and I love him very much.
I know that it is not anything to do with I feel like he using me for sexual favours, because I know for a fact that that is not true! He loves me in return and we have a great relationship outside of our sex life.

Help! What is wrong!?