We'll need to know if your period had been regular (or not) before this “light dark red brownish period” occurred. How long does your cycle last it was regular? If your cycle wasn’t regular, it is impossible to predict when the next period will come. A menstrual cycle should normally last 21-35 days. Menstruation (your period) typically lasts between 3-7 days.It doesn't seem that you are pregnant but you can take a home pregnancy test (you can buy one at the nearest pharmacy) to be sure.