Need help, really late.

I am currently on day 55 of my cycle. I was having unprotected sex. I had a blood test done a week or two ago cause I was in the ER. It was negative. I don't think I am pregnant but I have never skipped more than one month at a time. Any reason yall could think of AF isn't coming? Could I request an ultrasound to make sure everything is fine from my doc? And experience with false negatives?