Lying about Autism at Work

Hi,

This is the first time I write about this.

When going for my first job (as a waitress to give you an idea) the contract asked for any mental condition, I couldn't put I had autism down. It felt pointless to me to automatically put myself down as the black sheep. Nothing to do with shame but it felt that them knowing, I might react differently. It's been three months in employment and I am afraid of getting fired already because my autism is so well obvious. I've even avoided going to the dining hall because I am afraid my behaviour could scare the customers and I've been reprimanded by my boss twice due to my "rude behaviour" don't you know.

I am scared of what comes next.

The reason I am afraid to get fired is that I lied about my contract or that another unexplained incident about my behaviour could get me fired. And you can understand why I don't want to say "Hey I am autistic" as an excuse every time. I don't know what to do... when I am working, my autism and behaviour are all I can think of. 

Any advice on how to deal with this?