Anyone know why this happened? Almost called 911

Idk what to do so came here to ask. I almost called 911 cause I was just eating cereal and suddenly couldn’t breath like at all it was super scary. My first thought was I’m allergic because this was my first time trying that cereal. But as I go on my phone and dial 911 suddenly I can breath. I was super dizzy the entire time. Idk why this happened what is this? I have been stressed and over working myself. Now I’m just super lightheaded but I can breath fine.