“I love you, but I’m not “IN LOVE” with you.”
You want your spouse to know you really do care for him/her. The two of you have shared so much together, so naturally, you still love them as a person. You’re not cold-hearted and you don’t like hurting your spouse, but there has been a serious shift in the way you feel. You love him/her, but it’s not the same love you felt before.
Back before when the two of you started out and you were so in love you couldn’t get enough of each other. You felt so much passion you wanted to be together all the time. There was no way you could have ever imagined you would one day lose that feeling, but you did.