Super weird thing during sex?

To start off I am 14.5 weeks pregnant. While having sex with my SO, (geez I hope I can describe this accurately) I saw my belly rise on the right side and felt something hard, assuming it's the baby, every time he went all the way in. It felt really weird! He put his hand on it too and went in and out and we could clearly feel this THING rising to the surface of the right side of my tummy! Is that the baby?? And is that normal?? Just wondering because I googled it, and clearly since I can't really describe it very well I couldn't find anything. Thanks!