I used to feel like I was suffocating sometimes when I was trying to breathe... about a year ago. I have no idea why it was happened, but it scared me. I'm the type that keeps those kind of things a secret to see if they pass. Thankfully, it passed within the next year.... I still don't know what went on.
I'm sorry I'm not much help. Maybe ask if you can see a doctor? Hope its nothing serious.