I know what you are going through.
About 10 yrs. ago I had a GSD who became very protective of me. I absolutely LOVE those dogs- so regal and smart. But.....it was difficult. We finally had to take him to a obedience place where we left him for about 6 weeks. This was a place that specialized in 'aggresive' behavior in dogs, and was quite exspensive.
It worked and was worth it because this was a very special dog to me. However, it was almost impossible for me to keep up on, since I am too affectionate with my animals and had this tendancy to tense up when we were in situations where he could act-up.

It ended up being a constant worry for me when people were around.
What Carrie and KYS say is true. If you are a strong leader, and take the alpha role, it should be okay someday. I know it is difficult to NOT tense up in certain situations, but it helps a lot. I was never very good at it.

I think in my situation, I should have started working with him before things got bad. Don't wait like I did!
Good Luck to you.