BFP immediately followed by bleeding

I got my faint BFP Thursday afternoon (3 weeks 4 days) ! 
That afternoon into the night, I hate moderate bleeding. No clots. Cramping was equal to that of a period. Went to bed that night. Woke up at 3am dizzy, chills, crampy, still bleeding. Went to the ER. Ultra sound showed a little dot :)  HCG level of 12. Pelvic exam showed that the bleeding was fairly light at that point. Found out my blood type was O negative and had to get a Rogam shot.  Here I am a day later on Saturday still lightly bleeding. Holding on to all the hope I can. Have to wait until Monday to have HCG levels checked again.