HCG Rising but not Doubling (5w+3), experiences?

I had some very light spotting/cramping Tuesday and Yesterday so I got my HCG beta drawn a 3rd time. It went from ~1600 on Monday (Dr didn’t give me exact value that day) to 2670 on Wednesday... From what I read this is still within the normal doubling time range for this level of HCG but still concerned. No spotting so far today. Does anyone have experience with slow-ish rising HCG in week 5?

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