Life sure can suck sometimes sweety can't it. Like Tonya says, hopefully he will get used to the cast soon and you can help him decorate it up and make a fuss of how great it looks and then hopefully he will be proud of it and learn to love it.
You are obviously an amazing strong person from what I have read that you have been through so your lil man is so lucky to have such a great mum of which I am sure he repays you tenfold in love.
Hang in there kiddo as best as you can and I hope you have lots of love and support around you to see you through this shit time.
LOL
Mich xoxo