3/4 cup apple cider vinegar
5 drops tea tree essential oil
3 drops orange essential oil (optional, just for fragrance)
Put all ingredients in an empty yogurt bucket or similar container. Thoroughly rinse hair under warm water while brushing w/ventilated brush (widely spaced bristles w/slots between) or wide-toothed comb. Then fill bucket to near the top w/warm water and mix. Hold hair away from scalp, pour small amount of solution directly onto scalp, and rub in. Continue until entire scalp is done. Dip ends of hair in remaining solution and rub. Leave on for a few minutes, then rinse-brush again.
Works for me! After a few months of substituting this for shampoo in every-other washing, while gradually decreasing frequency of washing, I am now using this treatment only about every 10 days and no more shampoo. Saves a lot of time, and my hair looks great.

There's no telling what will happen postpartum though....
My hair is a little past shoulder length, thick, and wavy.