Should i be worried?

I had sex with this guy 12 days ago, and the condom broke. I’m on birth control but that particular week I had been really bad with it, because life was just too hectic. I took plan b but I have a feeling it didn’t work. I’ve been having random pains in my lower stomach and back, and this weird pinkish brown discharge. I’ve also been exhausted. I’ve been sleeping til around 10 am, when I usually wake up at 5:30 Am. I took a test but it was negative, but I’m afraid that’s just because it was too early to tell. I’m only 18 so I’m really stressed because I cannot have a kid. Please give me your opinions!