Once married I am sure you know that there are so many distractions with paying bills, raising children, stress, etc. People can change in a marriage because of it, but it doesn't mean they love you any less. We all get embroiled in our lives and sometimes we forget to take a good hard look at ourselves and our mates. We are the hardest on each other. The only true way you will ever know is by going for a walk with him (where it's peaceful) or go somewhere just the two of you and simply ask him if he loves you or is he unhappy in your marriage. There are always improvements to be made in anyone's marriage and we will never be perfect.
Good luck Marcy