Does Brown Vaginal Discharge And Pelvic/back Pain Indicate Pregnancy?

About a month ago i took plan b and i was fine then about two weeks ago i had sex and the condom had popped and he pulled out . I have been having brown discharge for a week and it recently ended. Now i have clumpy white discharge , im suppose to get my period sometime this week ... I have nausea mornings and nights and sometimes during day, i get some pelvic and back pain ... Am i pregnant ?