Rising but not doubling hcg level?

I just found out I was pregnant about 2 weeks ago and last week on monday I went to the doctor and everything checked out fine. I had my blood pregnancy test done and my level was 2500. Then on Wednesday I started bleeding heavy and passed a few clots I went immediately to the ER thinking I for sure had a miscarriage but surprisingly my cervix was still closed and the baby was still there. the doctor at the er did more blood work and my levels was 5404 so I was sent home on bed rest for 2 days and was told my levels should double in 48 hours. So come friday I went back to the doctor and had more blood work done plus I went to see my OB and had an ultrasound and found out I was right at 5 weeks and again the tech told me everything looked perfect there was a yolk sac and everything doctor did a pelvic again and my cervix was still closed. I have not had a sign of blood since the weds and only bleed for about 3 hours that day. but today i called for the blood test results from the appointment on friday and was told they where 5710 which isn't the high a rise should I be concerned my doctor isn't very concerned right now and has me on bed rest for a week with an ultrasound this upcoming Friday in hopes that there will be a heartbeat or at least more growth. Has anyone experienced anything similar with a positive outcome? I am worrying myself silly! Ive never had a miscarriage before and am just very concerned!