Gaining 90 lbs in one year is a lot. Have you had your thyroid checked? Before I had asthma, I did gain 60 lbs in one years because of my thyroid. I would seriously think about getting that checked if you haven't already.
Is your asthma managed by an allergist? If so, you might want to ask about Xolair. I take an injection monthly and I think I have been doing so for about four years. As severe as my asthma is, I have only had one ER visit and no hospital stays. If I have attacks during that day that I can't control, my allergist will spend several hours working with me in her office to keep me from having to go to the ER. Not many doctors will do that. I had to take early retirement last summer after I was diagnosed with epilepsy, since then I haven't had an attack that I couldn't get under control myself. I was working in an environmentally sick building at a university, but of course, they will never admit that. It has taken them 20 years to finally agree that the building next to the one I was working in was filled with mold and they are going to tear it down.
Of course you know you do not need to be working in the yard. That's probably just going to make your asthma flare, which means more Prednisone and more weight gain.
I hate the side effects of Prednisone, but as you know with asthma patients, it sure beats the alternative. I enjoy breathing, don't you?