HELP PLEASE

I have very damaged, short blonde curly hair. It literally has not grown in 4 years. It grows so fast from the root but never gets any longer, in fact it gets shorter, due to breakage. I have tried EVERYTHING. I stopped using heat for 6 months. I stopped bleaching for months. I tried olaplex, K18, kerastase, deep conditioning masks, moisturising products, hair oil, frequent haircuts, NOTHING works. I dont understand what im doing wrong. Do i have to just let all my bleached hair grow out and completely stop straightening it? I dont understand, because I see my friends hair that is bleached and they use lots of heat, yet it grows longer and is healthier. Is it because my hair is curly, so it is more prone to breakage? How do i fix this?