Could Sharp Pain In Chest Be Due To Prolonged Stress?

I ve once gotten an extremely sharp pain in my chest that felt like a heart attack so I went to the hospital. My heart tests came back fine. Since then I have felt my second rib down on my left be more prominent than any other. Almost as if it is swollen. I also get terrible pains in my neck and back That feels like my muscles are clenching and wont go away. I ve been getting sick as often as once a month with colds, bronchitis and pneumonia. When this happens I get so sick I m bed ridden, I have very hard times breathing. I understand that this night have something to do with my lack of muscles and low immune system. My doctor has suggested this is from prolonged stress and inactivity. I have a cold at the moment with a lot of phlegm which I try hard to get rid of. All this excessive coughing has caused my muscles to hurt more lately and it feels like I m falling apart. My real question I have though is about when I sometimes yawn I get these sharp pains in my shoulders and just tonight everytime I take a deep breath or cough I get a sharp ache under my top right arm. It hurts so bad but I have to continue coughing. It s terrible and I was just looking for another opinion because the doctors I ve seen (which are many) have not been very helpful. Information on me: I am 20 years old Height: 5ft 4inches Weight: 90-98lbs depending on the day My RMT says I have the back of a 90 year old with ridiculous trigger points.