LuvsChub04:
I get breathless after eating so ill lay down, thats when the tightness starts.
Burningburner:
this happens to me too it probably is from the pressure in your belly
Pretty much. Here's a diagram of your internals.
As you can see here, your stomach is partially in your ribcage. As such, as it expands, it can press up against your lungs. You might experience more relief if you are elevated instead of laying down.