Products to control the poof at the end of my thick, medium length hair?

I use shampoo and conditioner on a regular basis and my hair looks GORGEOUS right after I come out of the shower. It's straight as a board, soft and silky and not at all poofy. I don't blow-dry it, I let it air dry. Either way, it comes out poofy at the bottom that looks really ugly. I don't flat iron it, use chemicals or any hair gels/mousse.