Ask your doctor about it ... they know a lot ...
i remember once, it was numb in my chest and i had pain ... my arm too .. i went to see the doc cause i was worried about that, i thought i had heart problems ... but the doc look at me .. he went behind me and pushed in a specific place behind my shoulder and it hurts like hell in my chest and arm ... it was just a sprain muscle ... so she told me what to do and its fixed ...
that exemple just to say that human physionomy is complex but docs know all about it :) .. the sooner you'll get that checked the best it will be :) Also, worrying = stress and stress makes things worse ;)