It could be acid reflux backing up into your lungs while you are a sleep causing you to feel like you are unable to breath and also making you feel like you are having a heart attack........even if you don't have other symptoms of it, it could be silent reflux..........you may want to get checked for it..........:-) I am learning that it causes quite a bit of things for people.
Well, it could be sleep apnea. Or anxiety or the birth control. Sleep apnea is when your passages close up or something like that, and you wake up not breathing basicly. Have you been checked for that?