Had unprotected sex yesterday. My last per was on 1/29. If I take Plan B the next day, is that considered early & will it prevent pregnancy?

Plab B and pregnancy. Morning after pills, such as plan b, have their maximum effect if taken within 72 hours after intercourse. There is moderate effectiveness if taken within 120 hours after intercourse. Your last period being 3 days ago, indicates a low risk for pregnancy. Using Plan B early also assures a minimal risk of pregnancy.