Sorry this is really embarrassing but I'm. It sure if it's something I should be concerned about.
I have noticed the past few times I've had PIV sex I've had a really strong feeling that I'm going to pass wind or that my insides are going to come out of my bum! 

This also co insides with a constant feeling of fullness (like I'm constipated but I'm not)
I've had no injury or damage down there and no other symptoms of anything being amiss.
I've managed to clench for dear life to keep it in but it kind of kills it for me!
This has never been something I have experienced before and I'm worried it means something has moved inside to cause this trapped wind.
I know it's a known thing with some positions like doggy style (I didn't usually get it then either though) but this was missionary!
I know I have a retroverted uterus but as said this has never happened until now but it's making me quite self aware. This didn't happen after 4 children, my youngest is 5 and it's only the last 3-4 months I've noticed it.
I should add for the sake of stopping the comments, DH wouldn't care if I did fart, I could talk to him about it and be kind or he'd he'd find it hilarious and then take my lead on what I wanted to do about it, we're quite open as a house home about flatulence but I'd rather not do it during sex!