I've been riding for more than forty years. In 1996, I got back into biking after going through my teens and twenties, and I've been riding steadily ever since. But here's the thing...
EVERY SINGLE YEAR, when I take my bike out for the first time of the season, I damned near have a heart attack. I am lucky if I can get around the block without nearly blacking out from exhaustion and hyperventilation. I've always been in good shape and I weigh well under 200 pounds, but the first few years this happened, I panicked and assumed my riding days were over. The next day I would try again and I could get around the block 4 or 5 times. By the end of the week, I was riding 4-5 miles a day and taking 20-30 mile rides on the weekend. By the end of week 2, I'd be riding as if there had been no break at all in the action and I'd be planning a weekend tour.
I'm not sure why that first ride is always so murderous. Perhaps you forget how to breathe and how to pace yourself when you've been off the bike for a while. Try again, maybe when the weather gets nicer, your airways aren't filled with snot, and the air is easier to breath, in general. You're probably worrying for nothing.