Post Birth Control, TTC

Danielle
Hello!
So my husband and I are TTC #1. 
I went off the pill and had my withdrawal bleed end of July (25th exactly). 
I took ovulation tests and had a positive OPK on 8/12. 
6 days after, I had spotting and cramping for a week. 
Flash forward. No positive pregnancy test and no sign AF either. Last week I went to the OB/GYN and they did a sonogram that showed nothing happening cycle wise. 
Anybody else have a similar situation? Advice? My Dr. said to wait till end of October which is 3 months after stopping the pill to come back for a follow up, but I'm feeling anxious considering the sono showed no follicles, etc. 
Thanks!