Light brown discharge or spotting two days in a row. no sex in the past four days. the period shouldn't be here until next wed. no stress lately. why?

Likely hormones: In a 33 yo with normal menstrual cycles and no other symptoms, a little irregularity in the estrogen/progesterone cycle may produce early shedding/bleeding before the real period starts. Monitor this for another couple of periods. If it clears, no action needed. If it progresses, i recommend you see your provider for an examination. Menopause with its changes or other problems are possible.