I need some serious guidance. I don't know what is going on and I'm scared out of my mind!

Hi ladies, I don't even know where to begin. I was due for af on Tuesday. Took a pregancy test on Wed with a very faint positive. It just so happened I had scheduled a appointment with my obgyn prior to the faint positive because I was experiencing terrible pelvic pains. Did a internal exam and was not able to see anything wrong that would be causing this pain. It was also to early to see anything. The next day I woke up to cramping and bleeding very heavily. My doctor had warned me about a chemical pregnancy so I thought that's what was going on. Just now I took a few well alotvof tests and I'm getting BFP. If I experienced a chemical pregnancy why would the test be getting darker and why would I be heavily bleeding. I'm scared out of my mind right now.Please  help me.