Long High results without Peak

Hello, I've been using the Clear Blue Digital Ovulation tester for over a year now. I have been very conistant in my results from month to month, and normally ovulate around day 14. Last month was my first month trying IUI. However my ultrasound this month showed I have a thinner lining of my uterus than usual and we chose not to do IUI since it wasn't an optimal environment. Instead, I was directed to continue with natural methods. My ultrasound did show a mature egg and my OB expected I would peak in the days to follow. I started reading high on day 10, had the ultrasound on day 13, but this is the first time I have never reached peak. I am on day 22 and am still reading high. Is it common to have trouble peaking after an IUI attempt? If I did not peak, should my ovulation test return to low? Or is it possible to peak this late in my cycle? Most importantly for my case, I am low on progesterone and use my peak ovulation day to determine when to start using a progesterone supplement. We have been DTD since I started reading high, but I've gone passed my normal time to begin using progesterone and am worried it is all for not this month.