How to stop getting split ends?

I CONSTANTLY get split ends, I got my hair trimmed no more then 2 weeks ago and already EVERY. SINGLE. HAIR. on my head is split. and I don't just get split ends I get triple and quadruple split ends, and I've even had my hair conditioned with cholesterol and such at the salon and it doesn't help. I'm trying to grow my hair out to right above my butt, and I was almost there, but now that I keep having to get my hair trimmed, it's barely past my shoulders. also the cutters have no idea what they're doing because my hair is all different lengths now, the shortest length is about at my ear