period was 4 days late.. help!

My cycle is usually 29-30 days. Last month I took letrozole and had 2 mature follicoles so triggered on cd17. After that I was late for my period and thought I was for sure prego. Bfn on cd30. I spotted a little when I wiped on cd33. I then got cramping on cd35 and had what I think was my period. It was heavy the first two days with some dark red clotting and then a few days of spotting. I was super sad. Anyways yesterday I was unusually nauseous- I felt like I was going to throw up and had a headache... A few hours later I was fine. 

Is it possible to be pregnant and stil get your period? What has your experience been?