What Causes Spotting And Breast Pain After Intercourse?

Hi, I have a question about my menstrual cycle. About 2 months ago I had sex then a few weeks later I recieved my period. About a week before this months period I had some brown/pinkish spotting in my underwear that lasted 2-3 day and ever since there I have not recieved a full 5-7 day period. My breast werent hurting tell about a week and a half ago. I wondered what that brown spotting was and why my period hasnt fully come yet?