Good sex, but hard to get into the mood

I like my boyfriend very much. I find him attractive. And the sex is good. Still we do not make love very often. Once a week, sometimes twice. It is hard for me to get in the mood.

Afterwards I'm often surprised that it was so good; why don't we do this more often. And then again it takes a while. I don't recognize this from other relationships where I made love more often.

Is this normal?