Drastic reduction in compensation - Non compete

I joined my current employer 10 years ago and successfully built an entirely new business segment for them. And yes, I was stupid and signed a non-compete shortly after coming on board. The business segment I developed for them has become less and less profitable but it still represents a significant revenue stream. They now want me to focus on selling other services (which I do not believe offer a viable opportunity) and to "motivate" me in that direction, are cutting my residual commissions on my current book of business (which represents 75% of my compensation) to 1/5th their current level. The commission plan has been in effect for several years and they have made minor reductions to it over that period but this most recent decision would be devestating to my income level. There is one other sales person who's commissions are not being reduced - yet. (Technically, she's my boss in case that makes a difference). I'm hoping the fact that they are drastically reducing my commissions (taking away my ability to make a living) in some way invalidates the non-compete.