Definitely ask him. He may not realize that you're trying to get his attention, or there might be something on his mind that you're not aware of. For instance, my own husband was distant for a long time -- months, actually. I thought for sure that it must be something I did or didn't do, or perhaps he just wasn't interested in me anymore. It took several different tries and ways of asking, but he finally revealed that he had a number of health concerns. I didn't realize he'd been waking up multiple times every night with extreme muscle cramps, and he never let on that he had two minor heart attacks. He thought the knowledge would only scare me, but didn't realize that those issues and his reactions to them made a noticeable difference.
I'm not saying that your husband has something major going on, but he might -- you just don't know without communicating directly with him. Most men are notoriously bad at communicating feelings and perceptions, so don't expect that he'll even know the answer right off. By introducing your concerns, though, you might be able to get him thinking about what the underlying issue might actually be. Maybe it's just a bad day at work, or he just plain doesn't realize that there are other things you'd like him to do.