Hi Janet,
You're not going to like this. . .but I think the best thing to do is put this one aside and start over! Yeah, I know, I know, you want to throttle me. But what Mischa is saying is true. If you squint at the photo and painting you will see. You need to pay VERY CLOSE attention to the
large areas of light and shadow, and the exact value differences between them. Keep in mind that you can't break the light areas up with dark values. Everything within the light stays within a narrow value range. Same with the darks--you can't break them up with brushtrokes of too light a value. See in the photo how smooth the planes of her skin are? You are working too hard chopping it all up!
Oh, what I would give to get you in my studio for a day or two, Janet! You've got it in you, you know you do
P.S. I only suggest starting over because a) you can keep your present painting intact, b) you won't be distracted by the forms underneath, and c) you will avoid paint buildup. I did not mean to imply your painting is hopeless. On the contrary, you are
so close, but the problem is all over.