Had sex on 7th day of cycle then on day 18 had brownish spotting for 5 days then the spotting changed into bright red bleeding for 7 days with moderate flow then after that had pain in stomach back thighs gas constipation for 1 week on 12th January had yellow discharge and on 13th January had brown spotting for 5 days after that nothing and the expected date of menses is 22nd January I'm age is 22 and I'm very tensed is it related to pregnancy? What to do please help.