Don't freak out. You did nothing wrong, though I will second the comment that driving might not be the safest.
Maybe you should call the school and see if there is some kind of phone tree and someone else could help you with pick up and drop off for the time being. You're so close, some other parent might be willing to pull the assist for you until you can figure out why your oxygen is so low and walking is so hard. It can be a very temporary thing and I am sure you'd appreciate it.
Even IF CPS showed up, and I doubt they will, their only concern would be to just double-check that this is medical and not you hiding some drinking problem. Don't sweat that. As a former foster family, I've been investigated for...let's see....abuse, drug use, kidnapping, whether there are homeless people living in my attic, fire safety, etc. They show up, they are polite, they ask questions, they ask to see your attic...don't stress. A CPS investigation is about as low key as it comes. They are just there to make sure. And since it is the truth, you have absolutely nothing to worry about.
As to the person who called? Trust the rumor mill. The rumor mill was BUILT for this. Just tell the nosiest person you know. "God, such a rough week! I had this horrible chest cold, they pumped me full of steroids and I still couldn't breath! Hell, someone called the cops because they thought I was drunk! I was mortified. Fortunately, I just came from the doctor so I had all my paperwork and they totally understood. I am going back Monday for a follow-up and hopefully we'll have it sorted". I promise that by school time on Monday everyone will have heard the sad, kinda-funny, also tragic story about your horrible chest cold and getting the cops called and whoever did call will realize their mistake. Maybe they'll apologize, maybe they'll be too embarrassed, but either way you'll clear your name.
Or you can just keep it close to the chest and not worry about it.
In the mean time, lay down. Breath. Get better. Go back to the doctor if you're not getting better. No shame, no recrimination, no anxiety. You. are. just. fine. You did nothing, absolutely nothing, wrong. Way to go!