Could The Birth Control Pills Cause Irregular Periods?

Hey i had a d&c 3 months ago, and now im on Loestrin24 Fe birthcontrol (its only my 1st month on it) I had unprotected sex last week and the day after i came on my period and the blood was light pink and brown but it was only 2 days and usually my period is 7- 9 days. Could the Birth control have messed up my cycle? Or could i be pregnant?