Pain in left side of chest?

Hey guys, so ive been having a dull ache on the left side of my chest. Like right under my pec. Im not coughing nor do I have trouble breathing. Also when I bend my neck forward it stretches my back and I feel an ache right under my shoulder blade. I have been working out and dieting if that makes any difference. I cant seem to pinpoint where the pain is coming from or whats causing it. Could it be my back? or my chest? Ik nobody can diagnose my problem like a doctor can but any help will still be appreciated. Thanks.