Background check and employment

I have an interview at a job and I heard that you don't have to state or tell employers about past jobs so I didn't mention my temporary job. My mother told me not to say anything.

Reasons are: I got fired because I had an allergic reaction to Midol at work. They lied to me and told me, I won't be fired but 2 days later, I was let go.

I don't know if it was legitimate job or not because I was being paid in full without tax reductions. S

It was 2 years ago.

This is my first legit job and I'm now concerned that this will not get me hired. I trust my mother but I'm concerned