What Does A Negative Ultrasound Look Like Does Anyone Know Or Have Been In The Same Situation?

Does anyone know or have been in the same situation? - what does a negative ultrasound look like

I am 47 years old and had a tubal ligation 10 years ago. I recently had an ultrasound examination by the time of the last month was longer than usual. The ultrasound technician and radiologist said he seemed to be a gestational sac in my uterus, but not the child. I took a pregnancy test and blood was negative. The ultrasound and a blood sample was performed before I missed a deadline. Anyway, I want to know is ... Is there anything else I can look like imitating / amniotic sac, but not put the bag? When a cyst or a tumor? Or I could be pregnant, but this is the first test? I'm confused. I'm going for an appointment. in October, but I'm losing sleep to see what happens, and when I return to a mother!