Period two times in a month.?

Hye, im 20. i've never had this happen before. i had my period before, its was on 2nd of April, and then on 16 and 17th of April i was having an unprotected . And today, 26th April i'm having my period for the second time in a month. What's wrong with me? Can i know why? i dont know what to do. i dont want to see a doctor.