Period a month late! Had sex on sept 29 with a condom but ate plan be after within 3 hours. My period came oct 5th for about 5-6 days. But I haven't received any period after that which means its been 7 weeks since my last period (about 3-4 weeks late). I'm in school so I have stress and I also got a cold in the beginning of nov. when I was 3 weeks late, I tested 5 pregnancy tests (3 different brands) and all turned out negative. This Monday, I experienced bleeding (only a little on my undies) but it was bright red . Could I be pregnant?

Chances are very unlikely provided you've haven't had sex since that one time. The plan B will wreak havoc on your cycle and include stress and school, that is a recipe for highly irregular periods.

I would test again. Pregnancy is possible. The plan B isn't 100%. Test again using first morning urine, or get a blood test.

But, like Craven said, the plan B can throw off your cycle. Still, there is a chance of pregnancy.