I need major hair help please!/:?

Okay so about 3 months ago I had really pretty black hair that went down to about my mid boob area, and it was thick soft , and super healthy , then I made a bad mistake and wanted to try being blonde , well that killed my hair, I had to get it cut like right above my armpit, and it was super weak. After about a month of being blonde I dyed it burgundy and have been doing so since. Well my hair now is super weak and a lot thinner, and some of my ends are so bad that they actually look singed. And I JUST got a hair cut two weeks ago.. is there anything I can do that will strengthen it and replenish it to how it was /: So far I haven't been using any heat products and about twice a week I use a keratin mist. Anything else?