Inspiration Interupted

I have had this idea for a painting for a few years, I finally found the right references and had the right inspiration and so started it. I liked the sketch, so I started adding underpainting...NOW in spite of my measuring and checking several times and it seeming to be fine, it looks wrong to me! The head looks to big and I am NOT happy. Anyone else care to critique this? The right arm will be added in again, I just keep working to get it right. "Inspiration WIP"