Breakthrough bleeding

Hey ladies-I was supposed to start my period Saturday. I had light cramping all weekend, and some today, but I have started AF. Some other pregnancy symptoms (hot flashes, metallic taste in my mouth, a few others). When I pee, it's has been tinted with pink once and brown once. It's not CM, it's just tinted pee. Is this AF, or breakthrough bleeding? I took hpt yesterday but it was negative. Help!