I know it's hard, but Puppy's right - better to be honest. And if you don't like him wearing your shirts, don't let him wear your shirts!
Why don't you pick up that guitar again? Maybe if you channel all your energy into your music, you'll become a great blues guitarist!
"My H is a mean mistreater Wears my shirts throughout the day Oh my H is a mean mistreater wears my shirts all the live-long day I says to him, H One day you're gonna pay .."