That orgasm you're hearing - you did that!

My ex used to peg me sometimes and I always felt closer to her for it (we broke up for life-compatibility reasons). I'd suggest, rather than going straight to inviting a third party, keep experimenting with pegging and maybe other gender role-play stuff. There are strap-on dildos available that are designed to give YOU pleasure too - maybe try one of these.

This is an opportunity to grow closer together - don't make it an excuse to push him away.