I can't picture you as frumpy; you certainly haven't been in any of your WiWs here! But I agree with everyone else that this sounds like a problem of your outfits not reflecting your own personality and style, even if they're not frumpy.
When I think of your outfits on the forum, I think colorful, bohemian, soft, and playful. It should be totally possible to inject at least an element of that even into more "serious" outfits. I have the opposite issue to you... sometimes I find myself in outfits that feel too soft and feminine, and I have to remember to add at least one harder-edged element to make it feel like me (combat boots, a moto jacket, or something very structured). That juxtaposition of styles makes for an interesting blend. Taking the same idea but in the other direction, make sure you have at least one element of you-ness in every outfit... something floaty, or colorful, or that makes you smile.