From your post, your putting at least 1 1/2 cc of propionic acid ester in your shoulder.
That is a small area with far less blood flow, than say your quad or glute.
Generally, propionic acid esters are uncomfortable at any injection site b/c of the nature of the carboxylic acids.
My advice would be to stop injection in small muscles. If you are going to drop 1 1/2 cc EOD, cut the injection with the addition of some extra oil. I like cottonseed. Next rotate glutes stay out of your shoulders.