spotting on bc

hey girls! i’ve been having spotting / brown discharge for 7 days now. i take birth control continuously and normally skip my period for 3 months then take a week of placebo pills to have my withdrawal bleed. this time around, however, i’m deciding to skip a 4th month because i’m going on vacation. it’s now 3 days into the 4th pack, or when i would normally be having my placebo week if i wasn’t skipping, but i have been having this blood/discharge for 7 days. could this possibly be implantation bleeding? i take the pill religiously every day and haven’t skipped any doses. hopefully i have nothing to worry about but i want to make sure because my boyfriend didn’t use a condom the last time we had sex (one week ago). he pulled out (i think) but im still a little worried. thanks!