What Causes Delayed Periods After IUD Removal?

Hello my husband and myself are not trying to conceive at the moment. Iv two little boys. Had the IUd removed in oct and have had 3 regular cycles.length between cycles 33-34 days. It is now 36 days since last period. I did a test yesterday morning. It came back negative. It was from the clear blue advanced fertility monitor. We use condoms throughout the month but only put them on for the last part of sex. I m having period cramps for last five days.could I b pregnant? What s the next step? Too soon to go to go?