This might sound completely shallow at first, but it isn't:
Most probably, you're not physically attractive anymore. He loves you, so he doesn't leave you. But sex is a different thing. Sexual attraction is very, very physical. Maybe you've changed your appearance in a way he doesn't like (which includes growing fat)... or he sees your non-spruced-up at-home-look a little too often - that's something a lot of women seem to completely overlook.
So the other commenter's statement that "...there are so many guys who wants to have a relationship with me and people even strangers compliment me everyday. So that mean Is not me" is BS, really. Hardly anyone sees you the way your life partner does. Make sure he sees a hot version of yours most of the time (I could bet he doesn't at the moment). If he loves you, it's almost impossible for him to say "babe, you just don't look sexy most of the time" - but it's also hard to 'ignore' it.