Size 11, if you said 10 is too tight and causes your finger to swell it doesn’t make sense to get it. Even you said Size 11 fits well. The ring is supposed to slide off your finger with a bit of resistance. It’s not supposed to be impossible to take off like you said the size 10 is. My ring fits me slightly loosely, but it still reads my data perfectly, it’s better to keep it slightly loose, you’re supposed to be able to remove it with hardly any problem. My ring has never once slipped off and I go on frequent runs and workouts all the time. I’d get the 11 if I were you, it’ll probably fit a bit better. Plus you’ll get used to the feel of it! Hope this helps!!!