Delayed period or pregnant?

Ladies! Looking for some advice! First, I have the IUD. But my husband never ejaculates in me. We had sex on the 1st of March and he did. My period was due March 5th but never came. I started spotting on the 16th and that lasted 4 days. It started out brown and then a light pink and only showed when I wiped. I'm curious if anyone else is or has had this problem before. I called my doctor and spoke with the nurse. She laughed at me when I asked if it was possible I could be pregnant. I know all the things that can cause a delayed period. Maybe I'm stressing a lot? What do you guys think?