Pregnancy

Hi everyone.

I took 3 pregnancy tests and they all came back positive. I went to the doctor today to do a sonogram and they can’t see anything on the sonogram, I kinda have ideas on the days I had intercourse and was on December 11 and 13. Can anyone please guide me on what to do?

Last period was on November 20th. Could it be an ectopic pregnancy since they are not seeing a gestational sac?

Thank you