I know how scary that can be. With my second pregnancy I had some light spotting and it turned out to be nothing, but once I got a positive test and then a few days later I started bleeding like a normal period. Unfortunately in my case it was what the doctor called a chemical pregnancy, basically an early miscarriage. It happens quite often before many people even know they're pregnant.
If it's just a bit of brown or pink spotting, it can be implantation or irritation from sex, but if you're having full, heavy bleeding with clots and cramps like a period, chances are the pregnancy isn't continuing. Sometimes there are other reasons such as a subchorionic bleed, but only an ultrasound or blood tests can tell you for sure.
I'd suggest taking care of yourself, maybe doing another test in a few days to see if it's still positive, and contact your provider for advice and support. Early losses are sadly very common and nothing you did wrong. If the bleeding stops and tests stay positive, that's a good sign too. Either way, you're not alone and it's ok to reach out to your doctor to see what's going on.