I’m defeated. How to discipline a toddler

I remember before I became a mom, I was terrified of the newborn stage. It seemed so daunting.. the sleepless nights, keeping a baby alive. Ha. If only I knew how that was the easiest stage of all. Now my son is two. And I’m defeated. I feel like the world’s most terrible mom. I don’t know how to communicate with him; he doesn’t listen to me, he does things over and over even when I get on to him. I’ve done spankings, time out, yelled more times than I’d like to admit, and I feel awful. I know he’s only two.. but my stress is getting the best of me. How do I disciple a two year old?!