Therapist/Diagnoses/Mixups&Messes

I'm going to go to a therapist for the first time ever in a week or two, to get all of my sh*t dealt with. Like a LOT. I've never been, and this is a new, curious experience for me, and I think I'll start with a little bit of 'fun', with him/her. Picking their brain and such As intriguing as it may be, will it impede a full, successful, diagnosis? I already know what I am/have became, the problem is, will they? Who's been to a therapist recently?? Answers are kinda required.