I came on my period on 9/8/16 and came off on 9/10/16 now my stomach hurtin real bad breast still sore could i be pregnant it never did this before?

Maybe not, but...: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), 1 week after missing a period, or 1 week after starting a "weird" period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test.

Possible: Take a pregnancy test. Short period so perhaps just abnormal period if pregnancy result is negative. Rest and see how you do if worsens see your doctor