I'm concerned.

Well today I'm a little over 6 and a half weeks pregnant. I went to the ER Sunday due to bleeding and cramping. The ER told me I was miscarrying. I went to my doctor Tuesday for a transvaginal sonogram to make sure you uterus was cleared out but my baby is still in there with a heart rate at 55 BPM. The doctor gave me a 50/50 chance the baby will make it. My next sonogram is tomorrow. 
Has anyone else gone through this and carried their baby full term? I've been bleeding since last friday. It's red and brown. I'm so scared to go get my sonogram tomorrow. Any words of advice?