Tmi...pregnancy sex

I'm pregnant with my second baby, Around 17 weeks. My problem is that every time my husband and I have sex it is very uncomfortable when he is on top. He doesn't mean to and he tries not to but he ends up squishing my stomach and it Hurts. We try it with me on top but the problem is that I can't keep it up for very long before I get tired. 
I'm looking for any suggestions on positions that will not hurt my stomach.