Missed period for over 2 months but false pregnancy test

Hey so we are trying for baby number 2 since May. I have had a normal period since starting on May so 3 periods. In August I never started and still have not got my period I have taken a few tests but all have come back that I was not pregnant. I haven't had a period since July and am kind of getting worried and don't k ow if there is still a chance I could be or not. Anyone else had anything similar happen? Any advice will help. Thank you. I'm Barbara by the way ?