Standing to close is one reason for the shanks, but as I understand it there are many.

I was like you about 6 months ago and had them bad !! After an hour with the pro in the camera room we worked out what it was and how to adjust my swing. Basically my left shoulder was dipping and therefore moving me closer to the ball. It only takes movement of an inch or son in the wrong direction and you are in trouble. I would have never worked this out, so my advice to you...

Go see a Pro.