I'm sorry you're not happy with your relaxer. Some ladies have breakages w/ multiple textures, but I usually don't.
I have two textures now. I'm texlaxed (intentionally underprocessed) and 8 months post relaxer. I don't have breakage. Just because you're underprocessed doesn't automatically mean breakage. Make sure you're gently around the DL and I'd invest in some pure light proteins to add to your regular conditions.