withdrawal bleeding? pregnant? HELP!

i tried to skip my withdrawal bleed by going straight into another active week of birth control pills. this is nothing new to me, as i normally take active pills for 9 weeks straight. this time, however, i tried to skip a 4th month and i got breakthrough bleeding (very very old, almost black blood) for 2 weeks! i’m supposed to have my withdrawal bleed six days from now, and i’m wondering if i should still take the placebo pills that week or just skip it again since i was having that heavy breakthrough bleed for 14 days. i’m also worried i might be pregnant because the breakthrough bleeding started around the time implantation bleeding would start. it did last throughout the time my withdrawal bleed would happen though, so i think that means i’m not pregnant. implantation bleeding is normally light and lasts 2 days though so that just makes me even more confused. what are your thoughts? i’m only 16 and pregnancy is really not something i can do right now. i never miss a pill and take it religiously everyday. i’m so anxious about all of this because i’ve never had breakthrough bleeding for this long before. the last time i had sex was june 5th, and the bleeding/discharge lasted june 10th-24th. i’m almost positive he pulled out, but i still get nervous about this whole thing. i cant stop thinking about it. that’s also why i don’t want to take a pregnancy test because i have no idea what i would do if i was pregnant. i’ve been a little nauseas these past few days, but i can’t tell if its actual nausea or just nervousness. i’ve also had some lower back pain which is also making me nervous. my boobs are the same, and i haven’t had any other pregnancy symptoms, but i’m so scared. i know i need to learn to trust my birth control but it’s so hard for me because my ADHD medicine makes my anxiety 10 times worse. help! what’s wrong with me!