You should cut it but that doesn't necessarily mean you have to lose a lot of length if you like it. You could just add layers or give yourself bangs for more shape/texture. If you don't want the length anymore it could be a nice change. It really depends on what you want and what will make you happy. You have to look at it everyday lol. You could also just cut a little and see if you like that, then later decide if you want more cut. Its always better to be safe than sorry.
Probably cut it midback Girls with hair down to their hips usually have stringy, dry ends that look ridiculous. Just go mid back. If you still need a change, cut inch by inch on a weekly basis that way you kinda get used to the look.