I was in the same position in 2008, its very frustrating. I agree with Mark seek another doc.
My stim has worked great, it does take some getting used to. I have a Medtronic unit with 6 programs I can change, each give sensations in different areas. I found one that suited my needs and have never changed it in 5+ years.
I also experienced extreme pain from the trial site leads, awful things hanging outside the body. As active as I am amazed I didn't rip them out. It may just be your body adjusting to it. As far as rejection, that may be possible but they do use inert materials which the body cannot see or sense. Talk to your rep and doc about that.
I hope things calm down for you, my stim gave me back a somewhat normal life, even under the extreme conditions that were upon me.
Hoping to see a positive update soon.

German Shepherd Man.