Bill - when Val started Glivec 3 years ago, she had real problems for nealy 4 months with all sorts of things, including muscle cramp at night and tiredness resulting in her sleeping a lot during the day as well as at night. I can suggest a few things.
As you will see from these pages, tiredness is a Glivec side effect but if you are managing 30 minutes of walking a day after only starting Glivec a month ago, I wonder whether you could slowly increase the walking when you feel able to do it. Listening to your body is a great thing and try to be patient, however hard that is - it may take a while. It was nearly six months before Val could play 18 holes of golf all in one go. What sort of exercise do you want to do?
Cramps is another well known side effect. Some people take quinine tablets and others take magnesium but you should talk to your consultant about the options. If you can work with the consultant to find the right solution for you, you should be able to get rid of the cramps.
Good luck with it all.