How can I keep my hair healthy?

Hello doctor,

I am 21 years old, and I have been struggling all my life with how to manage my hair and maintain a healthy hair texture. My hair used to be curly when I was younger but then became wavy over time and for the most part, it is wavy (I feel like it would be slightly more curled if it was healthy). I used to have a lot of insecurities with my hair growing up. To the point where I cry about it sometimes even now. It is always very dry and tangly and I used to straighten my hair a lot to be able to manage it. But I stopped straightening my hair over two years ago due to damage. I feel like hair products I use (like leave-in conditioners and sprays) only help my hair for a few weeks to a month, it almost seems like my hair gets used to it and adapts to fight me back. I have used hair masks like olive oil and coconut oil but not consistently. Lately, I only wash my hair once a week (it takes a lot for my hair to get oily, and I only wash it more than that if I am outside where there is a lot of dust or dirt).

My diet is a lot of protein and carbohydrates (I work out 5 to 6 days a week) but very little greens (I am trying to work on eating that more). When I wash my hair once a week, I also lose a lot of hair, like 2 to 3 clumps, I do not have bald spots or anything, but I do get worried about my hair. I feel overall my hair is very fine, dry, and flat. It sits flat on top of my head with no body and it bothers me very much. I hate when other girls complain about their hair saying it is dead and they need a haircut, when their hair is way better than mine. I am going to have my hair for the rest of my life, I just want to know how to take good care of it and keep it healthy and put the right products so that I can feel happy, healthy, and confident.

Please help.