What Causes Brown Vaginal Discharge While Trying To Conceive?

I have had a brown discharge since 7 days passed ovulation (DPO) (using ovulation predictor), 34 trying to conceive #1, the brown turned bright red on the night (got up to pee at 2am) of 10 dpo just enough to fill the TP when I wiped, it was gone by morning (6am), and now back to brown, I'm now 5 days to my period. Last month I had a similar thing happen on 3 dpo till my period which was 3 days late. Is this something that may be preventing me from getting pregnant? or perhaps I was chemically pregnant last month? Or maybe I'm just getting too old to have kids... I had a total hormonal work up and doc says everything is good. Not sure if related but prior to that I was misdiagnosed as hypothyroid, 3 months later a specialist determined I was not, I was on thyroid medication for 3 months, this was 7 months ago. Your help is appreciated.