38 year old looking for answers

Morning everyone,

I have come to this forum in the hope of finding some answers / support. I have recently come to the conclusion that I may be autistic and I have felt a bit lost since. There are lots of reasons why I think I may be autistic but some of them are:

1. When there is too much going on around me (sights, sounds, smells, general input) my sense of smell completely disappears and I struggle to hear what people are saying to me.

2. I have had numerous burnouts at work over the last 6 years where my brain would just stop working. 

3. I only recharge when I am sat quietly at home on my own.

4. I feel anxious a lot of the time, mainly because I don't feel like I understand what the world wants me to do. As if I am playing a game but no one has provided me a rulebook, yet everyone else seems to have it.

5. I find enormous comfort in routine. I will often eat the same things at the same time of day every day. I will travel places the same way and I get very uncomfortable if that is disturbed.

6. When I am tired or overloaded with input I really struggle to understand what other people's facial expressions mean.

7. When things get too much for me I either shout or shut down and physically can't engage with anyone.

I am about a week out from my GP's appointment to try and get a diagnosis but as I said at the top of the message, I am feeling rather lost with it all. I'm looking back over my life at incidents that, at the time didn't make any sense (e.g. the way I reacted to certain situations) and Autism seems to give me an answer as to why I didn't respond Neurotypically. Yet at the same time I am looking at myself with fresh eyes and asking:

Which parts of me are the "real" me and which are the mask?  

What happens if I don't get a diagnosis?

Who am I?

It all feels like a lot to take in and I feel adrift, like I've lost my sense of self. Any advice from anyone who's been in a similar situation would be greatly appreciated.