Sex during pregnancy...

Hey! So I am pregnant for the first time and my boyfriend and I have slowed down with how often we have sex (we didn't really screw a lot anyway as he has bad back pain that most of the time causes him to not be able to ejaculate). Anyway I've noticed that if I'm on my back or something everything feels normal but if I'm on top every time we've done it like that since getting pregnant as soon as I start orgasming it's so intense I start crying. I assume it's my hormones and just wondering if this will stop? We find it easier for him to get all the way there when I'm on top so this is really putting a plug in the limited sex we have anyway as he's too scared to keep going. (Plus who wants a chick crying on them during sex lol) Please tell me someone else has had this problem too! I'm desperate as my libido is coming back full force haha