Anorexia and anorexia nervosa are not the same thing. Anorexia is a medical term meaning that someone stops wanting to eat for an unspecified reason.
Anorexia nervosa is a specific kind of anorexia. It means that someone stops eating because they're concerned their body is too fat to be attractive.
So, yes, it sounds like you might be in danger of developing anorexia, but not anorexia nervosa.
I don't think it sounds like it's due to "procrastination." Procrastination means postponing something you don't feel like doing, by trying to find excuses for not doing it. From what you describe, it sounds nothing like procrastination, and more like concentration. When you are very absorbed in doing something, as an autistic person, it's very common for your highly concentrated state to lead you to forget to eat, sleep, drink, pee, etc. This is obviously not healthy but it happens to me as well so I don't really have any useful advice I could contribute to help you stop doing it.