Please help! I feel like I can't breathe?

Help! Hurry! Around midnight or so, I started feeling like I couldn't breathe. Not like I couldn't get anything in, but you know how sometimes when you think about breathing, you realize that you're doing it and stuff? Yah, well a little bit later, I feel asleep and that happened twice and both times I woke up gasping for air. I don't think I was breathing in my sleep. My nose isn't stuffy or anything, but now that I'm awake and ever since my problem started, I keep feeling that feeling of how I need to make myself breathe. And sometimes I forget or am not concentrating and then when I come back, I feel like I was not breathing. Also, I feel a little sick and keep burping a little. I feel like I'm going to stop or forget to breathe and die. Please help. I really need to sleep and I'm afraid to fall asleep again or forget to breathe. What's wrong with me? I told my dad and stepmom. They said I'm fine; just stressed and am thinking too much. And my stepmom says it's probably PMS too. Um, I wouldn't know if it is or not cuz I've only had my period one time. It started last month on the 16th, so I should be starting again here soon. Is that really the case or am I going to die? Please help! I'm so scared for my life! I'm only 14