Severly damaged hair... help me!?

I have long fine but think hair that goes to my mid back. I have awful split ends that split pretty high up the shaft and also have more than one split on one strand. my hair is already damaged severely and I still straighten my hair everyday without a heat protectant. I know I should use one I just always forget and don't really take the time go buy any. i have never really cared to much about my hair's health when I was younger but now that I'm 15 I'm realizing how damaged My hair is! i only get one to two haircuts a year because whenever I go they always tell me how awful my hair is and then chop a ton off leaving me with short hair and I hate it!!!!. so on my next appointment I'm going to tell them to cut off all of my spilt ends and to make it look healthy and that they do whatever needs to be done. if some of the splits go up to an inch or so below my shoulder, how much hair do you think my hairdresser will have to chop off? I know it will probably be quite a bit..especially since my haircut won't be till summer and that means more damage! how short will the outcome be?