I was the deop shot I'm January of 2015 but I didn't take it February but I had my period in march but I had unpredict sex with someone I but he didn't nut me but I been cramping a little down their and been nausea what could that be?

Hello and thank you for sharing your question.

Any time you have unprotected intercourse, you have a high chance of pregnancy.  However, the brown discharge, cramping and nausea could also be caused by imbalanced hormones.

In general, the symptoms you are having are no cause for alarm.  Periods can be very unpredictable especially if you do not take birth control consistently. 

Faith