HI Orchid, firstly you are on "analogue insulin" not insulin. Of course excercise and altering your diet will help all of us type-1s, changing "insulin" may also help.
I'd been on synthetic insulins for 15 years when I was changed to Lantus. My blood sugars had always been erratic, but things went downhill fast, and I had no consistency day-to-day. I also started to think I was developing insulin resistence. However since I changed to pork insulin last May, I've achieved the best control I've ever had, and I feel better generally. If you think changing "insulin" is an option for you contact the IDDT for advice, tel. no. is on their website which is easy to find.
May not be the answer for you, but definately worth some serious thought.
Good luck
Jus