Confused about how far along I really am

Sandra
I had a miscarriage on July 12th, july 21st my hcg went back to zero. I had a blood test on August 29th that was neg. sept 4th I got a positive home test. My last ultrasound I thought I was 7w4d bit I measured 7w6d. I'm concerned because I'm on progesterone until  I'm 10 weeks and I literally run out of the medicine on the day of my 10th week. I'm just concerned.