Hi Liz! Welcome to the forums.
So let me get this straight, you took Pills for 8 years, then stopped when you broke up 4 months ago, then got back together and have been only taking pills again for a week/month or so?
In that case, there might be a chance you could be pregnant. Every time you go off your pill the chances of pregnancy go up. There might not be enough hormone for your body to protect against it. (Even if you were on it 4 months ago, your body could have started ovulating again when you weren't taking them.)
Some people say if you start the pill after your period then you are protected (Depends on the pill) but I usually say wait at least a month with a backup method for your body to become fully protected. I am always better safe than sorry though. You can still get pregnant while on your period but it's rare, but still a chance.
It could be breakthrough bleeding, or could be implantation bleeding as well. (Is it heavy or normal or just spotting?) In any case, to ease your mind you should take a HPT at 2-3 weeks past your last sexual act, at about the time you would be getting your period if you did indeed ovulate. That would be the soonest time for the HPT to accurately detect the pregnancy hormone. (Unless you get a super sensitive test) Just to be on the safe side