I've had a pain in the pectoral muscle. Right side just shy of the underarm area.
I would say No it`s not a pec tear. You are not lifting heavy enough to tear a pec, and if you had a tear, you would hear a popping, or tearing of the muscle, and would immediately experience a bruising look to the chest area and down the arm ( not pretty ).
It sounds like chest and shoulders are the bulk of your workouts. I would stop working the chest/shoulders group for a few days, and work the back, legs, abs etc. Don`t forget to stretch while working out, and always warm up prior to resistance training.
Thanks for the response SLERGE, it is greatly appreciated.