So on Sunday I did the OPK and got a positive result. That same night I had the normal cramping that comes with ovulation. Today I had a transvaginal ultrasound done because my OBGYN just wanted to make sure everything was still normal. She said she that she saw an ovulatory follicle on my right ovary indicating that I was ovulating today. I’m just very confused because I already had my positive OPK two days ago and when I took one today it was negative. Does anyone know what that could mean?

The photo in the comments is my negative OPK taken after my appointment