How much sugar in your cocoa?
You could try stevia. It has a pretty clean
sweet taste, but it does have a rather long
sweet aftertaste. If it didn't have that,
it would be the perfect sweetener. Many recipes
also need the physical properties of sugar
(aside from its sweetness), and sugar substitutes
don't have those.
I avoid sugar because it causes endothelial
dysfunction, which is believed to be the initial
event in atherosclerosis and is implicated
in type 2 diabetes. There is also a growing
body of evidence implicating it in the etiology
of Alzheimer's Disease.
Stevia isn't sugar, so no problem there.