Pregnancy anxiety

Ok so I’m 16 and I had sex with my long term boyfriend a week ago. I was on the pill, he used a condom, and afterwards I took Plan B because I was still nervous about potentially getting pregnant. I got my period a couple days ago and it’s not as heavy as it used to be and on the second day almost stopped completely and even though I know my chances of pregnancy are low, I’m worried it’s implantation spotting. I haven’t really had anyone to talk to about this so any advice is welcome