Saw the heartbeat but hcg isn’t doubling

Idk if I should be worried

1/18 hcg 39

1/20 hcg 97

1/26 hcg 1398

2/8 hcg 4262

2/9 topical ultrasound saw heartbeat

I am currently 6w5d based on last period 12/24, measuring 6w1d

Between the 26th and the 8th my hCG stop doubling, on 2/2 I had a doctors appointment and they did an inner vaginal ultrasound and said the baby was looking good. We even saw the flicker of the heartbeat, has anybody else had this happen where the pregnancy is viable but the hCG starts going up slowly? I’ve had no pain or bleeding at all