I posted something very similar in the 3b forum a few weeks ago... my hair looks very similar to yours. I can get volume by using products with glycerin, but then I get the frizzies along with the volume! If I just leave it alone, I get really nice spirals... but flat roots.
I've tried clipping, plopping, etc, but I have to choose only one: Either definition or volume. I can't seem to have both.