False Positive??

I was suppose to start my period Friday and didn’t, so Saturday I took a pregnancy test and it was positive. Sunday afternoon I started bleeding so I went to the doctor too see what was wrong. They didn’t really give me any answers other than my HGC level is 11 and the lowest is 6. She told me to come back cause I might of been too early to detect Hgc in my body. Or I couldn’t have been pregnant. But what would’ve caused a positive pregnancy test? Did this happen to any of y’all ladies out there? I just need answers 🤔