False test?

So i went to the doctor and they tested me for pregnancy and there was a faint line. I went to the hospital and got a blood test ( no results yet ) but I took a pee test I bought at Walmart and it was negative. I haven't had no accidents with my boyfriend. I've had my period every month. I take my birth control everyday and near about the same time. Am I pregnant? I'm so confused. Why would there be a faint line?