Could I be pregnant?

So about a week and a half ago, I had sex with my boyfriend and the condom broke. We made this discovery when he pulled out and everything went everywhere. He wasn't sure if he came inside a little or not, so we got Plan B. I took it 2 hours after the incident. I'm on birth control too (Tri Sprintec) and I'm on my 4th day of taking the placebo pill and still no period. I'm very stressed and nervous about this. I've never taken Plan B and lately I've been tired, moody, and not so touchy with my boyfriend. Please help!