Keep tearing a muscle in my right deltoid whenever I try and do push-ups, no matter how good a warm up I have?

This is really frustrating for me, I can do most other things with my arms, but the moment I try and do push-ups (with any hand position), I get a searing pain in my right front deltoid, and then it takes days for this pain to fully go away. I've tried resting up to a month without doing any push-ups, but the pain just came right back after I did the first one.