Well worry is a killer. The majority of guys here don’t have a problem but if you look hard enough you can find one. Its not unusual for all this concentrating on the dick to cause ‘Is this normal’ thoughts. If you are really very worried, drop the stretches for a while or stop PE for a week and see what happens.
The BTC is simple. Lean forward and bend your legs at the knee. Push the penis between the legs with one hand and grab it from behind with the other. Getting a good grip, pull the penis up toward the anus. The fist of the gripping hand should lock nicely between the cheeks of the arse. Then slowly straighten the legs and straighten up to increase tension.
Alternatively put one leg on a chair or bath or something loop the penis between the legs and make a good grip, then lower the leg to the floor.
Hope that helps.