Have you lost interest in having sex with your S/O cause you guys have been together to long?

The other night my significant other told me he was tired of having sex. We have been together for 13 years and he referred to me as the same black hole he has been poking at for so many years. We have always been very sexually active with one another and have great sex every time. He said he believes it's just cause he's getting old (31) but now I'm starting to feel like maybe he just isn't interested in me anymore. He has always done most of the work in the bedroom but it's not my fault he's good at what he does... lol. Maybe I'm letting it bug me for no reason but it really did hurt my feelings. After 13 years, 3 kids and our crazy work/life schedule I enjoy being intimate with him let alone even getting to go to bed with him since he works nights. I know he's not cheating but wondering if anyone else has felt this way about their partner after so long. Or did I just catch him on a bad day?!?