Birth control and plan b

So my partner and I have sex.. unprotected sex and we only used a condom once, yesterday i got birth control for the first time and i took a plan b, I’ve taken plan b before, this was my 3rd time, they lady at front desk told me to take the plan b and the birth control and i heard it’s bad to take plan b a lot, so i took it and the next day i went to the bathroom and i took a FAT DUMP (sorry) and i noticed my discharge is brown!! I’m freaking out why is this can someone explain!!