SOUNDS TO ME LIKE YOUR SHORTS ARE TOO BIG. THEY SHOULD FIT COMFORTABLY CLOSE TO THE SKIN, NOT TOO TIGHT AND NOT BAGGY. I'VE NEVER HAD A PAIR THAT STRETCHED OUT, EVEN MY LEAST EXPENSIVE ONES. I FIND BIKE CLOTHES SIZES, LIKE ALL OTHER CLOTHING TO BE INCONSISTENT, IT'S A NUISANCE FOR MAIL & ONLINE ORDERING...YOU MIGHT BE ABLE TO GET YOUR LOCAL BIKE SHOP TO ORDER CLOTHES FOR YOU-JUST BE SURE YOU DON'T HAVE TO KEEP THEM IF THEY DON'T FIT.
THIS MAY SEEM OBVIOUS BUT ... MAIL ORDER PLACES ARE USUALLY GOOD ABOUT STANDING BEHIND THEIR PORDUCTS. IF YOU CALL THEM AND EXPLAIN THE SHORTS DON'T RUN TRUE TO SIZE THEY SHOULD SEND YOU ANOTHER PAIR WITHOUT SHIPPING CHARGES AND PAY THE RETURN SHIPPING TOO. HAVE THEM SEND YOU A SMALLER PAIR FIRST BEFORE YOU SEND THE OLD ONES BACK SO YOU CAN COMPARE.