a few ideas here:
the simplest answer is its just muscle pain and working on them regularly will help. get a clock with seconds on it and time your self to set a base line, dont just hold the barre but mix it up with major minor and open chords as well as lead lines and scales. check your time once a week until you are satisfied. this is a great time to learn your keys so if you need to write out the chords for every key and every time you practice use a different key and use those chords scales and modes to both learn and getyou hands stronger.
another idea is to work on a warm up routine. figure out what works for you and what doesnt and get on with it. this is a strange idea but you might also check you diet. add some protin and remove some of the bad carbs/ junk food. even though this sounds strange try to take one day a week off from practice. dont even get your axe off the stand or out of its case, just relax.
another idea is try taking up video games. i know alot of guitar players out there are laughing at me but it can really help. the modern controller can really help build up that muscle and tendons as well as help with hand eye and abstract thinking. just try to avoid those guitar playing games, even though they can help get your timing skills better. just aviod computer games unless you have a computer controller with a thumbstick.play a few hours a week and in no time your hand will start to feel better.
you can buy a few hand aids that will build strength but you need endurance and flexability more than brute strength to play well. i know a few things about this because in high school i caught a katana by the blade in my left palm. i got 9 stiches nerve damage and muscle pain that never goes away.
just take your time and and itll come.
They say the END is near, but I'm Tired of waiting.