February 17 was my last period. when i got off my period i had an incident so i took a plan b. march 7th i had another incident and didn't take a plan b and i'm on no birth control. 4 days after the incident i spotted for 2 days. i'm now 3 weeks late. my

Do pregnancy test: Having unprotected sex places you at high risk for both pregnancy and STD. You should do a pregnancy test, and should be checked for STD(sexually transmitted diseases), which can cause menstrual irregularity. Plan B can cause changes in your menstrual cycle. If you are not pregnant, get some reliable birth control & use condoms, the best prevention for STD.