Looking For a Story

I hope someone can help - I'm looking for a story I read a while ago.

It was a bout a soldier (a sniper I think) captured by the enemy and viciously wounded in the groin.
He initially tries to continue as a guy but eventually changes over to female.
I cant for the life of me remember what it's called, or where I read it.
I may have got it on Amazon.

Any ideas?

Melissa