I had unprotected sex on the 15 . Neither I or my boyfriend was sure if he pulled out on time so we got plan b the next day . I heard I didn't need it because my period been off and had two more weeks until my next one. My period comes the 26 I've been having all the symptoms of my period coming but it 3 days late. Can I be pregnant ? I've read the plan be can cause your cycle to change causing it to be a week late or early . How true is that ?