Could my Dr be wrong?

I got given a clenil inhaler and a salbutamol one a few weeks ago because after a chest infection my Dr suspected I'd developed asthma.

I did peak flow measurements for a couple of weeks with the salbutamol inhaler and it seemed to improve things quite a bit with my peak flow scores at first.

Towards the end though I got 520/600 every time no matter whether it was before or after using salbutamol. Then I started the steroid inhaler and ever since it's just been the same score regardless of my symptoms.

I still have shortness of breath throughout the day in episodes. Using the reliever inhaler feels like it does nothing. I've just stopped bothering to use it. But my peak flow is the same even when my chest feels tight. It genuinely hasn't varied from either 520/600 sometimes since the end of the second week after my chest infection finished. Is it normal for it to always be the same score?

Could they be wrong about asthma? I have a spirometry booked all the way in April.

I have a diagnosis of POTS too and I'm wondering if it's that causing the shortness of breath instead because my blood pooling in my legs is terrible since the chest infection too...