Youre fine im 35 weeks and when i have sex My Baby likes to move to one side and ball up under My right rib (so it feels) as long as youre not bleeding or leaking fluid youre fine youll probably feel cramping though
Don't worry about it, unless you start feeling pain or your water breaks or something. You'll be okay, it's very normal.
Your uterus is just contracting :) sex, orgasms, and the sperm do that. How far are you?