from the top of my head to my waist I am as strong or stronger than most people but from the waist down I am weak as a baby..my feet move back and forth but not up and down..same with the legs..stopped walking 4/5 yrs ago...wheelchair 24/7 now...but move very fast in it!!!

One of my early symptoms was losing the ability to move my legs ( I did regain it) , keep trying and maybe you need a new Doc

I started physical therapy and that’s helping me a lot

It’s ms or weakness from not working out.
I would see a Neuro PT for an evaluation

Do you see a ms specialist?