What Causes Tightness In Chest And Difficulty In Breathing?

I have noticed a tightness at the back of my throat, that i ve not experienced before. it feels like my throats closing in almost, as i ve just looked in the mirror, i ve noticed the left side of my tonsils seem to have dropped - so rather than the entrance to the esophagus being a relatively symmetrical hole, it s now hanging down on the left hand side. i have no pain, and feel very well in myself. I have had some breathing difficulties recently where i feel very tight chested and out of breath, the doctor has put this down to stress but i don t feel i am stressed at anything. Could you advise? Thanks,