New IUD

Paige
Hi y'all! I need some advice please! I just got my IUD (mirena) put in last Tuesday-second day of my period. She told me to check my strings once a week to make sure all is well. I've been slightly bleeding and cramping since the process, which I've read was normal. But I tried to check my strings yesterday and....I couldn't find my cervix 😳. Now, just to be clear..I'm a sexually active 21 year old who's very knowledgeable about my body..and I could not, for the life of me, find it. I had my fiancé try too, and he couldn't either. Is this something anyone else has had a problem with? Should I be worried? Is it normal for the IUD to fall out/move in the first week? We had sex yesterday before that happened and now I'm nervous because of its not in place..well ya know. So I'm in desperate need of some advice and possibly some reassurance that this isn't totally crazy. Thanks ❤️