I used regular instead of lactose-free milk in the recipe while cooking for my lactose intolerant spouse. Now I see what happens, right?
What made you use the wrong milk during cooking?
I don't want to hurt his feelings, and I'm afraid that he will be upset.
It's wrong to knowingly feed someone food that you know will make them sick. Lactose intolerance isn't deadly but it still will make a person very uncomfortable and in pain if they consume lactose. It's best to be honest with your spouse and apologize for using regular milk instead of lactose-free while cooking.
I don't know if my spouse will be upset since I'm not going to tell him.
It's best to be honest about a mistake like this and promise to be more careful in the future. There's a good chance that your spouse will realize and mistake on his own. This could lead to unforeseen conflict in the future.