You said that you used to dye your hair every month...I don't know if you only dyed the new growth or all of it. But, the point is your hair is probably chemically damaged beyond repair because of your frequent use of dye. Kind of the same as if someone relaxed all their hair every month. Eventually, your hair will be past the point of no return.
There's not really anything you can do to make your hair healthy again if it's completely damaged. You could try protein treatments, moisturizing dc's, and whatever else. It may make it feel better temporarily, but it won't magically repair the damage. Also, flat ironing on high temps will only make it worse.
Unfortunately, you may just have to continue growing your hair out and chop off the damaged parts. It's probably better (and less shocking) if you trim little by little as your hair grows in. You could maintain the same length you have now and eventually you'll have only healthy hair left.
If your hair is damaged beyond repair, it sucks. But at least you're in a good place to move forward and learn what not to do in the future.
ETA: I just realized I posted almost the same exact thing in your other thread.
http://www.longhaircareforum.com/showthread.php?t=301453&highlight=
I knew this sounded familiar lol.