Any ideas? So confused

Last period was in the 21st August, now on cd45. pregnancy test negative. Had blood test yesterday to check hormones all came back normal. I have had cramps on and off like period cramps but still no af. I’m not in my country so when she carried out a vaginal ultrasound she said something about something being a little big (presuming my uterus) she said it could be one of two things pregnancy or period. Well test was negative and no sign of af. Should I just keep waiting? Pretty sure she said something about 20cm or could it be 20mm when measuring uterus not sure if that means anything. Any advice welcome