Why am I afraid of fighting?

I'm 21 considered to be a big guy, 6'2 and over 250 lbs. I NEVER pick fights unlike some of my friends I've only been in a few minor scuffles in my life when I was much younger. I have never truly punched anyone or have been punched in the face. I have no idea how hard I can punch or if I can even take a punch. I would take fighting classes but they're too expensive. Every time I think about fighting I always think of the worst possibilities such as becoming serious injured or getting shot or stabbed. I feel like such a weakling, how can I stop this?
Why am I afraid of fighting?
Post Opinion