You've lost some fitness just by riding little for a number of weeks. Recovery from that complicated by moving to the trike and learning how to ride it. Your respiratory issues are slowing down your return to previous fitness level, too. It's going to take a while. Be patient. Weeks, months...........as long as it takes. We lose fitness faster than we gain it. But, we can gain it back.
Took me at least a couple of months to acclimate to riding my first recumbent bike after riding primarily hybrids for years.