What's wrong with my hair?

I wash my hair everyday, because if I don't, then it will get all flat. I wash it just with conditioner every other day, and on the other days, I just wash it with cold water. It works good with my hair, and I have naturally curly hair, so when I get out of the shower, my hair's curly for the rest of the day and looks fine. But, the downside is that I can't brush my hair. I haven't brushed my hair in a LONG time, because whenever I do, it makes my hair go all flat and greasy. I can't towel-dry it or dry it with a hair dryer because it makes my hair matted. I need to let it air-dry. Also, whenever I wash my hair with shampoo, then it makes my hair really flat with no curls in it. I've tryed a bunch of different shampoos, but only conditioners make my hair curly for some reason. I also can't lye down without my hair getting all matted. Anyone have any tips on what I can do? Please help!