Losing interest, nothing in common

My husband and I have been together for 6 years. I'm 26 and he's 40. When we get home from work there's nothing to talk about or do. Our friend circle is very small and we like our personal space...kinda homebodies. He's always tired so on his days off he take 2-3hr naps about twice a day he said he doesn't know why he sleeps so much... He think it's age. I don't see him as "old" he's still fairly young in my eyes. Idk it's like I'm living with a zombie at times, but not sure how to have fun. I'm not into clubs,  I don't drink. We're very frugal so only go out to eat once every 2-3 months. Free things such as hiking I find boring. We get along as in we don't argue often  but we're just bored with each other...