Implantation on the implant?

I’m on Nexplanon and we use condoms, but I had some spotting about nine days after we had sex. The spotting lasted three days and was light brown. I’ve had spotting like that before and I wasn’t pregnant, but it’s really freaking me out. It’s been 12 days since the sex and I’ve taken a pregnancy test (I know its too early) and it was negative. I don’t know if I’m paranoid or if this is a legitimate worry. I just need some input.