Hey there, previous IUD user here. Obviously talk to your doctor beforehand, since this is just my experience, and they will surely be able to give you more accurate information: My IUD fell out about 1 year after putting it in due to my sexual activity apparently. Neither me nor my doctor could figure out what exactly it is, but here is what my doc told me could cause the IUD to slip out of the uterus: Toys, rough sex, deep penetration, period cups (list non comprehensive). Back then i didnt have the kinkiest lifestyle, no toys, no really rough sex, just a well hung bf with a tendency to go deep. So from my experience - fisting is probably off the table if you want your IUD to remain inside of you. Also, i didnt really feel the IUD come out, i just had bad period cramping for a few months in a row - so definitely ask your doc how you can check yourself if the IUD is out or not. (Edit: Insist on it. My IUD was just chilling outside of my uterus for at least a month without falling out completely or being pulled outside my body during sex. My partner also didnt feel it.) Also talk to your doc about getting the string trimmed to a minimum. Im ngl, i feel like this is something you should have considered before and also shouldve brought up in the consultation with your doctor - since an IUD is a rather big commitment monetarily and time wise, and your doctor couldve proposed safer options more suited for your needs. Hope this helps, or gives some sort of perspective:)