Etopic pregnancy?

Abbey

I have had my IUD since May 2017 and so far it has been giving me 3-4 week periods. I just ended one and now I'm having some intense uterus and anal pain and pressure. It gets really bad and then slows down and then comes back again. Mostly on my left side. I have been nauseous for the past month but I have also been starting a medication called Prozac which I was blaming the sickness on. Help?