Hey buddy, I don’t want to alarm you, I had a friend lose their cat very suddenly to a saddle thrombosis - which is a blood clot that can block blood flow to the rear legs and become catastrophic. It can happen suddenly and can cause loss of control of bowels, difficulty in rear legs, panting, expressions of pain from cat - ie meowing or howling. Did your vet mention/ rule this out when you saw them?
There’s a link below which explains it fairly well in layman terms. I hope it’s unlikely, it is very serious and early intervention is important and gives the best chance to your little guy. I’d feel bad having seen what my friend went through and not sharing the possibility with you.
https://www.thesprucepets.com/saddle-thrombus-in-cats-5199512
Jaime is an adorable floof!
I must know the source of your magic pineapple blanket that elicits these floompfs please?