Sex talk

Im 18weeks 1day. Me and my husband was having sex one night, he's always nervous that he's gonna hurt the baby. So when we was done. I was hurting really bad i laid down and the baby was at the bottom of my stomach sticking completely out. I could see a huge ball. And i was in pain for like ten minutes. Should i not be having sex so roughly? Or so often? We have two kids previous to this one. And ive never had this problem. Or felt pain like that. Anybody else having these kinds of issues?