i’m exactly the same. skinny and defined muscles (from swimming).
so i put on a new sensor this afternoon before swimming, and i had the same experience with it going completely wonky during my walk to the pool, my time at the pool, and on my way home from the pool. it is slowly getting back into sync again, but i will hold out with my expectations of immediate correlation to my meter until 48 hours have passed.(but who knows, maybe this one will be the one to start being in sync right away; fingers crossed)
nope. i had nothing over it and i didnt even bother using SkinTac. it stayed on tight.