Hi Vicki,
I'm sorry to hear you are having difficulties and can understand your frustrations.
What I think you ought to do first is take a step back. Have a day or two off and don't touch the guitar at all. If you want to keep your mind on guitar playing, spend some time browsing the Forum or have a poke around on YouTube . Just don't touch the guitar. Basically, chill out and relax..
You have been practicing far too much. Too much practicing is counter productive.
Practice 10 to 15 minutes at a time. You can do this 2 or 3 times a day. This will allow what you have learnt to sink in and give your fingers and muscles time to recover.
When you practice, take note of your posture. Sit or stand up straight. Follow Lisa's tips.
Warm up for 5 minutes doing Lisa's Spider exercise.
When you practice your chord changes, start VERY slow.Take time to place your fingers in the correct positions. Now play the changes,even slower than Lisa.
Keep a steady SLOW rythm. You are now beginning to develop your muscle memory. Do this 10 to 15 times very, very slow. When you can make the changes with no mistakes you can begin to speed up a very little and go through it all again. Continue like this and your speed WILL increase.
You can't rush this stage. It takes many repetitions to get it into your muscle memory but the rewards are worth it.
As your fingers harden up and your muscles develope things will become easier and you will go forward at a faster rate. Just don't be impatient.
As you develope you can increase your practice time a little bit at a time but I would say 30 to 45 minutes tops each session.
I'm 72 years of age and started this course about 5 weeks ago.I have made steady progress using this method The beginning was hard. But I've been patient. Now it is much easier.
I very much hope this has been some help to you. If you get any problems, don't hesitate to tell us on the Forum. We are here to help and make your guitar learning experience an enjoyable one.
All the best,
Joe