Don't know where to start re female adult diagnosis, head is tangled up mess

Hi, I'm hoping someone or one of the mods can help. 

I am female, mid-thirties and identify with a lot of traits on the autistic spectrum. This is something I have been aware of for three and a half to four years. I think reading and researching about it you could say, has been one of my interests. I have been a member of this forum for two years and stay on the periphery.  It has now got to the stage in my life where I want to seek a diagnosis. 

The catalyst for this being counselling therapy which I started yesterday. My brain and my mouth didn't match up. I found myself saying things which I now am not sure how true they actually were. We talked about identity and decisions.  It came across as though I had been coasting in life, when in reality the decisions I have made in my life have been very difficult to deal with. It was difficult to get much across because i was very emotional and i find it very hard to talk about feelings and emotions. Im going to end up rambling at this point to you so will leave it there for now. However, I can see this "delay" which I think is typical of me in that in order to understand my emotions and feelings, I need time to digest and reflect. The counsellor didn't know I thought I was on the spectrum; it was a 45 minute session and I had things I just needed to get off my chest. It's something I will mention at my next session. 

I have a good relationship with my GP and am currently reducing my dose of sertraline as the costs outweigh the benefits. I have mentioned the posdibility of AS to a previous doctor and she said it's something we can discuss and look into. Its on my notes. I would like to approach either of these GPs now. I know I will be asked "why do you think you are on the spectrum?". Well, how long is a piece of string?! 

The difficulty now is that, because I spend most of my waking life over thinking, and I have had almost 4 years input of ASC information, I KNOW in my head how my experiences can be explained through autism but am finding this very difficult to write down. There's too much to even know where to start. Because I have been flying under the radar all my life, and I would say I am a very internal person, I am going to have to fight my case, so I need things to come from me as coherently as possible. The therapist said yesterday (about another issue) it sounds like I can become paralysed by my thoughts and I think this has happened here.

I couldn't find the list on this website yesterday, but made three headings of social communication/repetitive behaviours/sensory to start off my notes, but like i said, notes are proving difficult to write. I have done questionnaires before but have found them difficult to answer as they seem to be aimed at stereotypical behaviours.

I just feel like a tangled up mess. I want to move forward with my life and this is the next step but I don't know where to start. There's also the risk I don't get a diagnosis but I will cross that bridge when I come to it.

Thank you for getting to the end of my ramblings.