What to expect with post coital???

Ashley • Married June 2013. Momma to 3 furbabies. 🐶🐶🐶 December 2015 our lives will change forever. 😊👶🏽.
I am having a post coital procedure done tomorrow and for some reason I am nervous about it. I was wondering if anyone here has had one and can tell me what to expect. Is it painful? What does it consist of exactly? Thank u in advance!