What Causes Brown Spotting And Dull Stomach Pain After The Period?

hello, I started my period about a week and a half ago . it was very light. now at almost ten days later i am still spotting brown and i feel a very dull pain in my right lower abdomin and lower back on the same side. i recently switched birth control and i have had sex on my period when it was really light like almost nonexistant. but we used a condom. do i have an ovarian cyst or could i be pregnant? which one of the two seem more likely