Spotting for 5 days, no period.

I am 29 yo and trying to conceive my first child. I stopped taking the birth control pill 4 months ago, and my cycles have been 35 and 37 days, and now I'm on day 41 with no period and no cramping but I have been having brown discharge for the past 5 days. All HPTs have been negative. I chart BBT and use ovulation predictor strips, and both confirmed ovulation in October. Is this spotting an indication of low progesterone? Since I'm trying to conceive, what can I do?