I'm currently going through my second round of EMDR. The first time was almost 10 years ago, then new issues arose and I went back to it as it was so successful the first time. There are many times that I feel worse for a while before I feel better. It takes time to process what comes out in a session. I agree that it has to be done properly, though if not done properly, I don't see that it can do any harm. Some sessions are more effective than others, some leave me drained and exhausted, but I've never had a 'bad' one.
Share what you've shared here with your T. I, too had some doubts at times, but now I have no regrets as I am certain that my PTSD would be much worse had I not kept going. I control how hard I push myself and know I can stop a session at any point if it gets too intense, but I usually push through the rough stuff because while I know I will be exhausted afterward, I also know that while processing the session afterward, I learn more and heal faster.
Good luck and I hope it works as well for you as it has for me.

WW