Possible Misdiagnosis: Seeking Advice on Autism

I think I may have been misdiagnosed with a cognitive disability. I believe I have autism actually. I just had a full on meltdown over something so small in my car. I've never not had meltdowns. I've had them from as early as I can remember until now at 24 years old. I also have a hard time understanding simple things like multiple step instructions and my ex roommate and ex fiancée both used to tell me I don't know how to sweep or mop properly. I also get overstimulated very easily. My mom said I've always thrived off of routine and this is the first time I'm actually thriving off of no routine. I think I need to go see my neuropsych again. I know it's so hard to be diagnosed as an adult though.