Weird periods

My last period was on November 27th, which means I’m now going on a 41 day cycle. I get my period every month, not on the same day but a period every month. I’ve taken tests, they are all completely negative. I’ve had on and off spotting (I’m talking like a tiny spot of blood on the toilet paper) My doctor said the only thing they can do to regulate periods is birth control, which I don’t want to do because I’m currently TTC.