How to check IUD strings?

So I'm not very impressed with my gynecologist. I had my 3rd baby on March 4th, on May 13 I got my first IUD. I just had sex for the first time since getting it two days ago and then had sex again yesterday. Both times at first I could've sworn I felt something and it was a little uncomfortable but only for a minute. I remembered my Gyno casually mentioning that rarely an IUD will fall out. So I googled it. And everywhere I look it says my gyno should've told me how to check my strings and that most doctors recommend checking them often in the first few months of getting it. On top of it I had to reschedule my 6 week IUD check and the soonest date they have is August 3rd! I also read you're at higher risk of your IUD falling out if you get it shortly after giving birth. I was about 2.5 months postpartum and I know my cervix is always slightly dilated at this point from having 3 kids (was told by a doctor). So anyways how do I check the strings just so I can make sure my IUD isn't coming out and how often should check them?