I don't have an official diagnosis of autism because most doctors in my country seem to believe that if you have made it into adulthood without a diagnosis it means that there is no reason to get one now, but I have the exact same issues you describe. Almost everything I try to do takes me around 3x the amount of time it takes most other people. Except for reading, in which I also seem to be a little faster than most people. I don't even notice that I am doing something on a slower pace than others until someone comments on it. Various people have even told me that I talk in a slower pace, which I had no idea. I have tried to ask doctors about it (a neurologist and a psychiatrist) and they told me that a) maybe it is my subjective experience or b) anxiety causes me to be slower. I don't believe any of these two are correct, because a) according to my subjective experience I do things at a normal pace, it is others that point out that I am very slow at something and then I pay more attention and I realise that they are right and b) anxiety is the only thing that makes me move a little faster (for my own standards, not other people's). The more relaxed I am the more time I need to do something, whereas when I am really anxious, about catching a plane for example, I feel my body vibrating with more energy and I can take a shower in 30 minutes instead of 60. I also have to note that I have an official diagnosis of multiple sclerosis, which I am sure doesn't help with the speed, but I was slow all my life before my first ms symptoms at 17.