HCG doubling but....

I feel frustrated! I’ve had 4 draws so far

4.1 - 115

4.3 - 254

4.5 - 549

5.0 (today) - 1148

My numbers are doubling in 48 hours, but they’re only doubling by a little bit. My Dr NEVER seems satisfied when he calls. I wasn’t expecting to have to go in again today, but of course when I talked to him Saturday, he wanted another draw. I’m assuming it’s because my number are either on the lower side (even though they’re within every single chart range I’ve seen) or because they’re not doubling big amounts. I’ve asked him every single time if the Number is ok and he always says “yes, it’s just a very early pregnancy”. Then why does he have me keep going in?! I know I’m going to have to go back on Weds and most likely Friday this week. Anyone else have experience with their hcg number doubling but only doubling by a little or having lower numbers? It’s hard to get even a little bit excited. I’m dreading the phone call from my dr tomorrow 😏