Could you be confusing love with passion, excitement and lust? Because those things can fade a little in a long term relationship, although they can certainly come back. After the initial honeymoon stage it's normal for your feelings to deepen into a more solid love, which might not feel as exciting but should feel stable and enduring. Some people have an idea that love should always be wild, passionate, painful and exciting but I'm not sure that is sustainable in the long term.
After several years I still love my partner although it is not the same as when we first met. It feels much stronger now, it's a bit like building a house the wrong way round. You do all the exciting things, the décor and the furniture and other more superficial things first, and then the foundations come later, the solid, lasting basis for a successful relationship.
If you are not sure whether or not you love your partner, or whether or not you love him enough then he might not be the person for you.