6 days late, negative tests, U/s showed fluid in uterus

I am never late but I have had two blood tests and they were both negative. I've had a lot of cramping and I had an ultrasound which showed some fluid in my uterus, which they think could be from a cyst bursting. I got meds for my pain and nausea and now I'm just an emotional mess waiting for my period to get here. How can I track anything if I don't get my period? Is there any chance I really could be pregnant? The pain is bad but the confusion and frustration is worse.