Apparently this was the same with me. According to my (long dead) granny anyway. I do other things left handed, like playing pool/snooker. Although my preferred wanking hand is my right haha.
My handwriting is awful, I write in capital letters just using bigger ones for the letters that are actually supposed to be capitals, fuck knows why, my dad does the same, just felt natural & as soon as I stopped being forced not to I automatically switched to writing like that.
I also hold a pen weirdly, where most people would just put their index finger at the front of the pen I put my index & middle finger there (does that make sense?), which means it starts to get painful quite quickly if I have to write for any length of time. Fortunately god invented computers so fuck handwriting!