A pastor's wife AND a doctor?

If God has called your fiancee to be a pastor, then either you are also called to be a pastor's wife (uming it is His will that you marry). God will not call someone with a spouse into a service without calling also the spouse to it. What role you choose to fill in that position is not up to God, but up to you. Personally, I don't see any reason you couldn't or shouldn't have a medical career if that's what you feel you want to do with your life. Do what you feel led to do. God doesn't call us to do things we wouldn't like or enjoy.