I will get this random pain under my left pectoral muscle, it's sharp and quick doesn't stick around for very long. it occurs maybe once every 2 week?

Musculoskeletal?: Fleeting sharp chest pain lasting only seconds, worsened by movement is usually musculoskeletal in nature. For ex: a young man who does upper body weight lifting may strain his pectoralis muscle, causing fleeting sharp pain. See doc if pain is associated w/shortness of breath, or palpitations, lasts longer than a few minutes, or increases in frequency or intensity, or does not resolve.