HCG levels

I’m currently 4 weeks and 4 days. I’ve had the HCG levels drawn three times so far. I was told they need to at least double ever 48 hours. From my first test to the second they more than doubled but from my second to my third they only doubled 59%. Has anyone experienced this and is this a cause for concern?

Test 1 at 4 weeks: 194

Test 2 at 4 weeks 2 days: 499.1

Test 3 at 4 weeks 4 days: 797.9

Please help, I’m so concerned.

UPDATE!! My last HCG test went from 797 up to 2,100!!✨ next up is my first ultrasound to see little bean!