pregnant??????

ladies please help i'm freaking the hell out. so two weeks ago on july 4 i took plan b because the condom broke. I've been on birth control for about a year , the only reason i took plan b was because i'm not positive that i've been taking bc at same time everyday. After i took plan b i bled for 3 days. I've been continually taking my birth control and leading up to today i noticed a lot of brown blood or spotting? i'm scared of what's happening? Maybe my hormones are just crazy messed up from bc and plan b? or what! opinions please