3 periods

[sbonfiglio]

ok i was on birth control since i was 16, well for the last 3 months i have been off it. Well I had a period dec. 10th...went through about a five day cycle and was done, well a couple of days later, I took the plan b pill becuase of an incident the night before. well a couple of days later I had another period, it was another 5 or 6 day cycle and was heavy through out the whole cycle and that was during the xmas time. Well just yesterday I started another, this one is a little lighter but its been within a months span i have had these 3 periods, give or take a few days. Now what bothers me is since i have taken the plan b pill i ended up have unprotected sex a few more times and didnt take anything after. So Im worried if I was pregnant, how am i suppose to know when i keep having periods, and a good sign im not is becuase im having so many periods in a small period of time. should i go to the doctors?