Slow rising hcg?

Does anybody have experience with slower rising hcg? I’m not sure exactly when I ovulated. According to my LMP, I’m 6w6d today, but think I might have ovulated later than day 14. Here are my betas:

1/25- 25

2/1- 672

2/10- 2426

2/15- 4118

My fertility doctor doesn’t seem concerned at all, but I can’t help but worry. I feel like if they were more concerned, they would’ve had me come in every 2 days, right? I’m not having any symptoms of concern, I’m having all the usual pregnancy symptoms.

I had an early ultrasound at 4w5d and saw gestational sac only, but the doctor said that’s perfectly normal that early. I don’t have my first OB appt until next Tuesday.