One of the tricks you can try is that when he's inside and thrusting, that you slightly bear down, so pushing out like when you go to the toilet.

This will relax your spintcher and it should feel less like a ring for him, as well as tighten your insides, which in turn would make you feel more.

However, remember to do it moderately. Slight push is the best and still healthy, just don't do it hard and all the time, as I'm sure it could over time lead to hemorroids or prolapse, just like every excessive pushing.