I think you've been given some good advice here. I would say just be very gentle but matter-of-fact about it. Make it clear that you in no way mean for him to feel like you don't want to be around him, but just like anybody else, you need some "me" time now and then. At the same time, don't over-do it in your explanation, if that makes sense. In other words, if you over-do it with reassuring him that there is no problem in your relationship, he may take that to mean there IS a problem. So, just be very matter-of-fact, but again, gentle. Sorry. I hope that makes sense. ;-) Not really sure how else to put it.