Children this age are vulnerable to temper tantrums, pal. If you don't know that, then I have to ask why you got pregnant and had a baby in the first place, because you obviously aren't mature enough or educated enough to be able to raise a child successfully. And being spanked sends all kinds of messages to kids, most of which are really, really BAD. For one thing, it tells the child that hitting people is the best way to solve problems. It also tells kids that it's OKAY to be violent and aggressive toward anyone they don't like. In your case, you showed your son that you were and are a BULLY, and someone to be FEARED. Kids who learn lessons like these, especially BOYS, often grow up to become domestic ABUSERS as adults.
Please see your doctor and ask him or her to recommend a therapist or mental health professional, so you can get some help for your anger issues, and your son can get some help with his issues too. HE needs to be evaluated for Autism, among other conditions, and the sooner the better.