What Causes Heavy Bleeding During 5 Weeks Of Pregnancy?

I was 5 weeks and 5 days pregnant last Wednesday when I had to go to A&E as I started bleeding quite heavily - I was told after having an internal that my cervix was closed and u was bleeding from outside. Doctor said they couldn t rule out miscarriage but also mentioned erosion of the cervix. I had to go back the next morning for a scan and the technician saw a 5 week old gestational sac which he said is in the middle of my uterus and has given baby 1% chance of survival. He mentioned my progesterone levels were low but I won t know for certain until I have another scan on 25th. I am still bleeding, no cramps only had mild period pains for a couple of days and feel a bit nauseous. Is there anyway I could save this baby? Anything I can do to help, ask for i.e. Progesterone injection? Can the sac move and end up where is should? Thank you Sharon