I went to the doctor after having small cramps and what I believe to be implantation bleeding and it was light pink and went to brown, only lasted one day. I had an ultrasound and the technician told me there was a small sac but nothing in it yet. Okay so I go home and a few days later I start bleeding, starts out brown and stringy and next day it's dark red. Not really any bad cramps. I don't know what is going on I'm just trying to get pregnant again since I had a miscarriage last year. Please help?