ERP Experiences?

I've been told by my first T that I have all the symptoms of PTSD but "not the criterion A" (because I didn't tell all of my trauma, probably shouldn't have hidden it), and my new T said I do have it. I feel like I have to give a disclaimer, sorry, my OCD makes me unsure of whether or not I have an official diagnosis.

Anyway, my new T said ERP could help with my post-traumatic stress. I've done it with OCD, but never with my trauma. My T is a trauma specialist so I know she knows what she's doing, but I'm still extremely anxious about the idea. Has anyone had any experiences with ERP? I just want to know what I'm walking into first.