How come my sim's "mate" will not sleep in the same bed with my sim, after they have "woo hooed"?

I invite my sim's special love interest to spend the night, he gladly accepts, they end up woo hooing (3 times to be exact) and when it comes time to p out. The lover walks around the house all night crying for sleep but talking to himself in the mirror, taking showers, playing guitar in the bathroom, but doesn't even attempt to sleep with my sim or even on the sofa. What's going on? I know he can get in the bed because of the woo hoo's.