I hit my 3 year old today... 😭

We were outside, eating a hot dog and I was making sure she was chewing each piece well. She ate the last piece and suddenly got really quiet. I was watching her and I swore she started changing colors. In a split second, I was sure she was choking and my initial reaction was to whack her really hard on her back. She startled and looked at me so wide eyed and hurt, like she couldn’t believe what I had done. She still wouldn’t talk and I was saying her name and asking if she was ok. She looked at me, about to cry and said ‘I was just thinking, mom.’ I apologized to her and explained that I thought she was choking, but the guilt I am feeling is so heavy right now. I just can’t believe any of that happened and I keep imagining what she must have thought and felt in that moment with me hitting her out of nowhere. I’m a mess and I have to vent. Nothing like this has ever happened to me as a parent. I know I had no ill intentions, but the way she looked at me and how she’s probably aware that I can hurt her now...I’m just beside myself.