Well its probably because you've straightened it to many times, literally burning the hair leaving it with no cuticle.
The one thing you need for smooth hair is cold water, it does actually close the cuticle and rinses better than warm.
Also a shampoo with natural ingredients, they may be expensive but some can be pretty
cheap. If you can't afford the expensive kind go for Suave children's shampoo gentle and smells great.Â
