What Causes Tightness In Chest With Difficulty In Swallowing?

I have a really uncomfortable chest, it feels tight, and when i swallow it feels like there is a lump of something at the bottom of my throat, it feels almost like some food, or a build up of phlegm. It is not painful just really uncomfortable, It gets worse when I lay down to sleep, and I am beginning to feel light headed and sick with this too. What could it be?