You're seeing a doctor, so I won't reiterate.
I had the same thing happen this past Fri/Sat. I have a clockwork seasonal allergy that occurs Late May through most of June which I've narrowed down to tree pollen. They're worst at home where I have two black walnut trees. It's usually just itchy eyes, runny nose, and tons of sneezing, but your exact symptoms happened to me on a rec ride into headwind on Sat. It was a little scary, but it went away, and I've had no issues since. I attribute it to allergies, but I'm curious what your doc says. I'm overdue for a checkup.