Trouble breathing?

Mackenzie • Kenzie. 19. Married to Khalid 💍.pregnant with my first child. September 1st 2015 😍
I'm only 16+6 and I literally can't BREATHE. I'm always out of breath even when I'm lying down trying to sleep! It's to the point where I get light headed and start getting a really bad headache. 
Does anyone know why this is happening and how I can cope with it?