Could you write it all down? It might be easier to explain to the fitter that it is hard to talk about and hand them a written description. They will still have to ask you questions, but it might be a way to get started.

I'm not sure where you are at, if it is a small town it might be harder to find someone, but often physical therapists will do bike fits as well. Would it be easier for you to go to a medical professional and maybe even find a woman?