chest and shoulder pain

Hi I am 19 years old and suffer from mild asthma I never really have attacks I just breath differently, the reason for this post is because I have been suffering with really mild chest pains for the last 5 to 6 mounts, and my doctor has put it down to my asthma being activated by a chest infection, this has been my diagnosis a few times and have been put on antibiotics, which help but I am still having these pains, and in the last few weeks it has become alto worse and mainly located on the left of my chest and my shoulder along with mild shooting pains in my neck and both arms. This occurs every day but mainly as a discomfort not pain but at night it is alot worse and when I am in bed. It dose not cause any coughing or shortage of breath but sometimes I feel like I can't unconsciously breath and have to force my self to breath out. I have smoked for about 5 years on and off and because of this I am worried it might be something serious, and was wondering if any one else has had these problems and might no what it could be, thank you.