Very slow HCG rise. Panicking!

I'm panicking. Started spotting red blood on TP when I wipe, nothing coming through to pads. I went in for HCG levels and on Thursday they were 3794, but 48hours later had only rose to 4196. I had an US in the ER that measured me at about 5.5-6 weeks though by my calculations I should have been 7.5 weeks based on LMP. I'm looking for any glimmer of hope or success stories of a slow rising HCG and spotting leading to a healthy pregnancy!