What Causes Late Periods With Brown Discharge?

My last menstrual cycle was May 3rd. Last week i have been symptoms as if i would start my period. On friday the 28th of may, i felt as thought i needed to make a bowel movement but everytime i would go to the bathroom nothing would come out. Usually when i feel as though i would start my period i would make a bowel movement and would start my period. The second round of going to the bathroom i noticed a couple spots of brownish discoloration in my underwear and that is all i noticed. Today it feels as though i have started my period but it is very very light. My husband and i have been having unprotected sex a few times. The week of our honeymoon we had unprotected sex about 4 times that week and when we got back from out honeymoon May 3rd is when i started my period. advice?