I Ve Been Having A Constant Discomfort In My Left Chest, Please Help

Chest pain/discomfort, shortness of breath and throat full of mucus, HELP PLEASE! Hello, this is my first post, i m Michael and i m 18. I ve been having a constant discomfort in my left chest for over 2 weeks now, the first time i felt this i went into a panic and was taken from school straight to the doctor , he checked my chest and told me my heart and lungs were fine, nothing to worry about, however that was 2 weeks ago and since then i ve been having every so often sharp pains in the area of discomfort lasting barely a few seconds, it is like a constant dull ache. Along with this dull ache is a constant need to take a deep breath, as if i m constantly out of breath and also a constant build up of mucus in the throat that i either need to spit out or swallow which had been going on for 3 weeks, a week before the chest ache, this has gotten quite annoying in the past few days causing my throat to feel like its blocked, a constant feeling that there is something stuck to my throat. Other on and off symptoms include an ache in my triceps and shoulder , pins and needles in my hands and legs and an on and off headache that had been going on for a week now. I would like to get some replys as to what people believe it could be, if anything, is it worth revisiting my doctor again after he said i was fine just for what could be a bad case of the flu? Your replys would be most appreciated, thank you Michael