I was having a problem with breakage, but it was from dryness. Protein treatments tend to make my hair even dryer.
I get shedding, but not more than natural daily shedding.
The only thing that seemed to have stopped breakage for me was clipping thin ends, washing every few days, deep conditioning everytime and moisturizing daily. I always use the same products.
I get NO BREAKAGE! After years of breakage, I cannot believe I can run my finger through my hair and not have any on my hands.
But, yeah, for me the intensive treatments make my hair too dry which can then cause breakage for me.