Try not to take it personally Jill although it can be difficult. I had a client who was exactly like this.
So I asked him what the issue was in a very diplomatic way and he said " I've always been like this after sex, I tend to fall into a deep depression and just want to be left by myself".
The condition is actually quite common it's called Post-coital tristesse or post-coital dysphoria (PCD) which " is the feeling in humans of melancholy, anxiety, agitation or aggression after sexual intercourse".
Hope that helps