Your pecs and delts originate from the clavicles. It sounds like you are overly tight. You might need better nutrition, to just get used to it, or you might be injuring yourself. There's no way for us to know. If it's tolerable, I'd just keep working out in the hopes that I get used to it.
But before you do, make sure your form is 100% correct. I really messed myself up in the past with that same combo.