I think it is reasonable to want your partner's undivided attention. It is also reasonable to let him multitask if you are just talking about the mundane details of your life. If what you have to say is important and significant, make a point of pausing, taking a breath and making eye contact. Tell him that you really need him to hear what you are saying. There is a fine balance between wanting his attention (or anyone's attention, really) and demanding they listen raptly to every word you speak. When you're just chatting, loosen up a little. When it's important, make sure they know.