Hey, I'm so sorry that you are so scared. I want to play doctor here and remind you that the more upset you become, the more difficult it's going to be to move air.
How do I know this fact?
I'm the QUEEN of shortness of breath. When they do my lung volume test... they always double check the machine!! 20 years running... ha.
My lungs aren't the same as other lungs so they can't move as much air. Every breath I take is labored and takes a lot of energy. If anything is near my mouth/nose, I get a little panicked b/c I can't suck in as much as I need to in order to get air.
The good news, even though I have to work harder than most people, I am able to maintain a healthy blood oxygen level almost all of the time! It does "feel" like I can't breathe... but I'm moving enough air for my body to do what it needs to do and my guess is that you are as well, or you would have been admitted.
Patients are triaged when they go for visits and breathing difficulties have become at the top of that list in recent years... at least in the US. They finally started to take it seriously after losing a lot of patients who didn't present as trauma but were indeed suffering tremendously due to a breathing difficulty.
Over the years, I've also learned that though breathing is automatic, it is heavily affected by me and my thoughts and behaviors. Just the same as running a mile will up your respitory count... so will becoming upset and anxious. If you already have to work hard to move air... that extra stress will just make your task that much more difficult. So, in that vein, it is very important that you stay calm.
It sounds funny but I'm very serious... think about ninjas. Think about any dedicated practitioner... breath control is a HUGE part of their skillset. Influence over an automatic process is powerful... always. I've surved many asthma attacks by refocusing my energy, being calm, and saving my energy for each breath despite the pain and urge to panic.
So, that being said, I feel suffocated right now... it sucks so hard and I do understand your worry... I'd recommend you buy yourself a home monitoring kit if you can afford it. You can get a pulse ox monitor for under $100. Use it when you start to feel short of breath... choose to feel better once you see a strong number reflected... or choose to get immediate help if you see it drop to an unhealthy level (decide this w/your doctor, everyone's baseline is different).
If I would have had that option, I would have chosen that path for myself instead of learning the "hard" way...
Good luck. Feel better soon.