Welcome to the forum corignani. Really hard to answer your question without actually seeing you shoot as the list of possible causes could include one or all of the following; sloppy release, bow arm torque, collapse after release, overly closed stance and/or wrong size shirt (just kidding). Want to clarify on your form overall?

Where is your anchor point. Normally to be catching anything around the shoulder tells me you are over drawing your bow.

Troy

Corner of the mouth is a good spot. Still, you are most likely overdrawing by extending past 180 degrees with the alienment of your body. In other words your bringing the bow arm past the alienment of the chest. Try bringing the bow arm slighly inward a degree or two and see if this doesn’t clean up your problem.

Sounds like your standing straight and pulling the bow. If so, your form is just slightly over extended.

Troy

I occasionally have trouble hitting my shirt on my bow arm side if my shirt is loose fitting or there’s a wind at my back. I try to keep an open stance ie bow arm foot pointing outside of the target slightly.

I have that happen to me as well. Usually the culprit is what wTk mentioned, baggy shirt and wind. I always carry an extra elastic with me to slip over my arm in this situation. Works like a charm.