In need of advice

So I have the skyla IUD and it expired earlier this month and I get it changed this week. I'm late on my period by a week now and I've taken tests and they all come up negative. I was told that if I wanted to on the iud that I could take plan b if I had unprotected sex or it expired to just be safe. Could that be the cause of my issues? I also get UTI's all the damn time