Is it a heart attack if your having chest pain, but it goes away when you lay down?

I have been feeling a fullness in my chest. I went to a chiropractor and they said its probably from my neck being out so bad. Also, when I lay down all symptoms that I do have go away. I will be 41 in june. However, my dad died at 37 and my sister at 33 both from heart attacks. just wondering if it goes away if you lay down if it could still be a heart attack?