DepressedCurls is right. Your best bet is probably PTs followed by conditioning DTs and lots of tender care. And sorry if I'm stating the obvious, but you might want to consider growing the light parts out instead of continuing with touch ups.
When I unwittingly wrecked my hair the same way recently (with a shot of uber peroxide), I used Joico's K-pak (protein reconstructor) once a week for a month. Good luck.