What Causes Sharp Pain In Chest Radiating To Underarm?

I m an 18 yr old female and I ve had pains in my chest and underarm for a few years, but in the past month they are getting worse. The underarm pain is an ache-like pain- it almost feels like something is blocked but it spreads down my arms and into my back and ribs. The chest pain is very sharp and sudden right below my ribs, and I have to take very quick breaths when it happens. I ve also been getting out of breath for no reason- I ll be sitting down and suddenly I m gasping for air. I eat very healthy and exercise and the only real health problem I ve has was a melanoma in-situ about a year ago.