I Get Chest Pain In My Lower Chest Near My

I get chest pain in my lower chest near my sternum when I lye on my back with my head propped at little with pillows. It seems to be worse if I eat peanuts or popcorn. If I move to my stomach or side for a while it will go away, but if I get up move around it goes away faster. I am female 48 yrs old 5' 94lbs. I have severe neck/spine problems, I also have acid reflex. Do you know what could be causing this?