Help! Chemically damaged hair!

My hair is naturally thick and curly, and quite a long time ago, I chemically straightened it and ruined it!
When I towel dry it it puffs up into a huge unmanageable frizzy heap (though it looks straight when wet)

I have gotten around this problem for a while by applying mousse/gel after every shower. My hair does not puff up then, but remains looking straight.
(This is a drag, I want wash n wear hair)

I`ve tried applying countless rescue treatments and hot oils but my hair has not recovered! I have not even seen any sign of progress.

Can anyone help please? This ould be greatly appreciated.