What Causes Difficulty In Swallowing?

I choke often - sometimes on food and drink, sometimes on nothing I am aware of, sometimes when I try to sing. I am aware (I can feel it) that at times my epiglottis does not work right and food goes into my lungs. I cough and cough but it is dry and unproductive. I am not breathing well. I can never predict when an attack will come - it's painful and every breath is uncomfortable. What should I do??