Light brown/reddish spotting & vaginal itching/discomfort one week before period is due. i was on antibiotics for sore throat last week. what could be?

Sometimes a woman : Can experience overgrowth of candida when on antibiotics. A clumpy (cottage cheese- like), white, non- odorous discharge associated w itching, burning, swelling or redness can be due to yeast infections. It doesn't usually cause spotting. If you have a change in color, texture, odor or amount of vaginal discharge ; problems such as pain, itching burning with urination or sex or redness/swelling.