low hcg levels. Rising but not doubling.

Christina
I've had 4 betas done so far. Last Monday it was 24, weds 48, fri 79, today 155. I'm not sure what to feel or think. The numbers aren't doubling but are rising. I go back Friday. Anyone else go through anything similar with a positive outcome?? I'm not sure exactly how far along I am. I miscarried on July 29th and got my bfp on August 26th or 27th.