Brown discharge and then nothing

Before I start it might be TMI but we’re all women here right? So anyway: I get brown discharge before every period and then usually the day after I get my period. About two weeks ago, I had sex with this guy and even though we used protection, the condom didn’t break (he did the inflate the condom trick and no air leaked out) and he didn’t even ejaculate in the condom til after he was out of me, he made me take Plan B to be sure. So I know a lot of you may laugh at me but am I being paranoid? Is the Plan B just offsetting my period that bad? I’m supposed to get my period in two days, but I’m very irregular (i have skipped a month while I wasn’t sexually active). I ask that you please be nice and if you don’t have anything nice to say then don’t reply.