It sounds like you were having a panic attack. There is a quick breathing exercise that works well for me. Find a safe place where you can sit down and be alone if you can. Breath in through your nose slowly for a count of 7 seconds ( 1-1000, 2-1000, 3-1000, etc.) filling your lungs completely. Then hold your breath for 7 seconds. Then exhale out of your mouth slowly for 7 seconds. Your breath should be expelled completely around 7 seconds if done at a correct pace. Give or take a second. It takes a little practice so don't give up. Then repeat until your heart rate has decreased. It usually takes a minute or two of doing this to bring your heart rate down to a normal rate. It also grounds you in reality as you are focusing on your breath. It's hard to do anything but panic when your heart rate is up so high. So just simply focusing on bringing your heart rate down will improve all of your symptoms bringing you back to reality.

P.S. Panic attacks can be exacerbated by caffeine, lack of sleep, hunger, dehydration, pms, stress obviously. Make sure all of your basic needs have been met. Sometimes just assessing yourself for a minute can help you identify what has set you off. Knowing is half the battle. Often times we can correct something to help soothe our panic. Having said that, sometimes there isn't an obvious reason and that is ok.