Period 2-10aug.had sex in afternoon on 15aug.light brown colour blood stains were noticed on 15aug night and 16aug night only.i don't feel pain at all (except when having sex on 15aug,i feel like my labia/virginal was hurt when he come in) normal or?

Common problem: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections & hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.

See OB: See your OB. Pain during intercourse followed by light bleeding may indicate a vaginal tear. Be careful and educate yourself about sex, pregnancy, sexually transmitted diseases you can get from men, and how to get your partner educated, tested, treated. Lubricant can help you from feeling pain during sex. See this video:http://www.cdc.gov/std/be-smart-be-well/letstalk.htm