Yelled at my two year old and his response killed me

I'm sure everyone's had moments like this, but I just need to vent because I'm so sad. I have a wonderful little boy who just turned two - let's call him John - who is super sweet, very active, and VERY verbal, his language is really developed for his age. I think I'm pretty patient, but like any toddler parent I've lost it from time to time. I try not to yell but I think most of the times my son has heard me raise my voice is when he's hurt me. I know he's a toddler and still learning boundaries, but there have been times that he's hit me or almost hit me by flinging a heavy toy around, and my knee-jerk reaction is to shout "No! No!" I always apologize after and explain that mama was scared, we don't use our hands for hitting, etc. but in the moment I sometimes freak out and shout.

This morning I was just fried, I'm PMS-ing, I was trying to get my son into a clean diaper and clean clothes so we could get out of the house, and he was rolling around on the diaper table and kicking. He kicked my hand, which banged it into the wooden divider on the diaper table and really hurt. I shouted and he said "What John do?" Again, I tried to calmly say I was sorry for yelling but that really hurt mama, we can't roll around on the diaper table, but I just felt awful. I don't know if I'll be able to unhear him saying that ever.