Exteremly damaged hair?

I have very very curly, thick hair so i straighten it almost every day. i've been doing this for about 3 years straight. When i first started straightening my hair it was thick and healthy. A year after i started realizing that when i straighten my hair there's a lot of hair on the ground (and i mean alot). Now i straighten my hair and there's more than ever hair on the floor, and the breakage can be whole strands or strands that are 1 to 2 cm long. My hair is breaking from every single point there can possibly be and its gotten soo thin. I can't curl my hair because it looks like a disaster even though ill do it if it makes the condition better. What can i do to repair my hair? Will it ever become that thick again? and do i have to stop flat ironing it completley?