Hi wj,

take a break!! If you practice 3-7h a day it could mean you are pushing yourself way too hard. You are trying to do things faster than your brain can process it at the moment. Changing cords on the fretboard fluently and fast is a combination of muscle memory and brain - and for this you need to allow time. Pushing it is not going to work and you will get frustrated (went through this stage myself years ago).

Take two cords and change between them for no longer than 5 minutes in a row (perhaps a few times a day with breaks). Then play along with a song of your choice just using the base cord (only one cord) to accompany the song (that's to put your mind away from cord changes). Alternatively you could just listen to some music :-)

The danger of practicing 3-7 hours deperately and tensly cord changes will do only one thing - you get frustrated and the brain get the message that it's not working at all and blocks any further progress.

Take a deep breath and sloooow down. You will be surprised how much better it will work after a couple of days break. Don't make practicing a chore - make it fun!!

Best wishes