Fetal heart beat monitor??

I may sound crazy but I havent been on since end of july and all test are negative. I was going though my things and found the monitor that I had with my son so tried it out and found a heart beat at around 140, i even did a test this morning and was negative, what should i do? What should I say to docs so they can give me a ultrasound? Do u think they will if I tell them this x