Hello, Regular unprotected sex has greater chance of being pregnant. You must undergo one blood test for beta-hCG to exclude early miscarriage as all above features are quite common in pregnancy. Beside pregnancy, there are several reasons of brown discharge like hormonal imbalance, pelvic or vaginal infection, stress/ anxiety, old blood or endometrial tissue, irregular diet habit etc. Here, you may need to undergo one pelvic ultrasound scan and hormone test to pinpoint the diagnosis in the absence of pregnancy. Treatment depends on underlying etiology. Consult with your gynecologist at the earliest for other relevant investigation if any. Avoid stress, take healthy diet, control body wt, maintain genital hygiene properly and take proper sleep. Be well & take care.