could I be pregnant??

So I have had an IUD for a year and a half and never had a period with it for the first year but after that they were regular every month. Me and my boyfriend have a pretty regular sex life and he cvums insdide of me every time because I have an IUD. this month my period was supposed to start on the 16th and it is now the 20th and still no sign of it. last week I would get really weird cramps at night but no bleeding. could I be pregnant? looking for honest advice. :)