NEED HELP! Hair is dead

My hair is so unhealthy. I started straightening my hair in third grade and continued to straighten my hair EVERY SINGLE DAY until just the beginning of this summer. I dyed my hair three times my entire life, once I bleached it. I have so many dead ends and my hair always falls out when I get a shower, or run my finger through my hair. I have curly hair so a lot of the times if I don’t wash my hair everyday it gets huge knots that hurt to detangle. It’s also really frizzy from all of the split ends. My hair is so dry and coarse. I don’t know how to make it healthy again. I’ve heard that trimming it doesn’t do anything and I don’t want to try it anyways because I want my hair long and thick, which it is already really thick. What are some tips and tricks that I can do to help my hair. Im no longer straightening it because I’m serious about making it healthy again.