I was about 8 years old when I saw "The Fly". It was a double feature at the Bay Theatre in Baytown, Texas. Also playing was "The Alligator People". Both of those movies scared the crap out of me. I had stepped on a 'rusty nail' and was afraid to tell my parents for fear I would get a shot. At the move, scared spitless and watching the movie through my hands over my face, I told my older brother I had stepped on the rusty nail. He told me that stepping on a rusty nail would turn me into one of the Alligator people. I was terrified. I began to demand he take me home,...getting loud in the theater. We still laugh about it to this day....53 years later.
I saw it at the theater in my hometown in SoCal (in Texas now...got here as soon as I could). My sister worked at the boxoffice so I got in to all the movies for free...How great is that for a kid!!??
I am just a few years older than you. I had the same reaction - it scared the crap outta me.