21day progesterone test

Hello Ladies,

I have a question for you all this is my 3rd cycle on Letrozole and this time I took 5mg. I have a 34 day cycle from my calculations. When I do my ovulation test on the 21day (bloodtest) my levels are low and showing that I didnt ovulate, but my cycle has been coming..monthly. So when they are doing the blood test on the 21st day could it be that I havent yet ovulated? Or that cycle day isn't the best day to test for my ovulation since I dont have a standard cycle? Just wanting some opinions and advice for my next doctor's appointment.