Second filter.
We've all made bad decisions that we thought were good for us at the time. Don't judge yourself too harshly for that.
If it were me? I'd err on the side of telling him. We both know how it feels to have memories missing. This isn't quite the same thing, but there's power in learning the truth. Relief, too. Even when it hurts.
Besides, think of how relieved you'll feel when he finally makes peace with what happened. When he forgives you. He can't start that process until he knows.