I was due to do an IUI cycle this month, I was taking Letrozole 5mg for 5 days, but my 3 follicles stopped growing at 10.8mm so my cycle was abandoned. I was on Progynova for my lining, which worked (reached 8.2mm - in the past it's been about 6mm). My partner and I continued to have intercourse (unprotected) after the IUI was cancelled but now my period is 4 days late. I haven't rested yet, but wondered if it could be the Progynova that could be causing the delay?