Has anyone experienced this? Ever since I had my son I get severe numbness and tingling in my left arm. I always carry him using my left arm It increases if I hold him for long periods of time.

I've experienced that too. I used to carry my baby using my left arm as well as I'm more comfortable with it and my baby is easily sleeps but I had no choice but practice to carry him using both arms alternately. Otherwise, my left arm would get numb every time I'd carry him and worse, I might drop him if I don't feel good about my arms.