tvc you make me think you have the flimsiest body ever 
I have a low constitution stat. But I'm also kinda indestructible. I do and have done horrendous things to my poor body, but aside from being a bit prone to getting sick and getting minor injuries, everything turns out fine.
That is odd, are you sure it's a muscle related problem? It shouldn't take months to heal if it were when there's no apparent cause.
The initial injury was an achilles tendon injury, and they can take up to a year (or more) to fully heal. It hasn't constantly been in pain, it gets about 90% better, and then I will re-injure it. I haven't hurt it again since I switched from shoe to boot, though, so I think it's getting better.
There are recommended exercises for such injuries, but I ain't got time for that shit.