Intercourse one week after period, 3 days after intercourse i got brown discharge for 5 days, then stopped, now my period is late. hpt are negative. whats happening?

Late periods: It depends on how old you are or if you have had intercourse within the "danger" period, but check another pregnancy test in 1 week to be sure. Irregular potting indicates hormonal imbalance which may be natural as you age, or related to a number of other factors, including stress, nutritional variation, anemia, etc. Recommend you visit an MD clinic to be checked out.