"Brittle" Type 1 Diabetes

I have pretty much been able to eliminate blood sugars above 170 mg/dL, but have been struggling to keep them in a comfortable range between around 85 to 125. I swing quickly and easily between below 65 to above 135.

I've been told that my Type 1 is "brittle" and was wondering if others have been called "brittle"  before.  What do you think it really means and what can be done about it?  I'm on a lo-carb diet and count carbs, I exercise regularly and I'm on a pump.  What else can you do?