My boyfriend and I have been together for over 4 years. He's 40, I'm 42. We only see each other privately one day a week, because of his responsibilities with his kids. We do also spend time together, meet for dinner, talk a lot, etc outside of that day, but we have one day a week that we meet just the two of us in private and generally are intimate. My boyfriend has a habit to "warn me" days in advance that he "might not be up to sex". He also mentions a lot during the week that he hasn't felt much up to sex, or hasn't felt very sexual, or similar. It seems that the more flirty or sexy I behave when we talk outside of the day we normally get together, the more he tells me about his non-sexualness. It's really beginning to get on my nerves, because as soon as he says he might not be up to sex, I start trying not to want or expect sex when we see each other and it completely kills my libido. Generally, when we do meet, he does want to get sexual and I end up trying to push myself back into a mood that I've killed because of this advance setup of expectations. It's getting worse and worse because when I start looking forward to getting intimate, and tease him or flirt with him, he seems to feel pressured and give me this warning. But then he does want to have sex and, you know, women lead up a lot and the pre-flirtation and anticipation is kind of part of the foreplay. So if I'm just not thinking about it, not talking about it, and not expecting it, chances are I'm not going to just be ready the minute he decides he's excited after all. But when I tell him this, he gets upset and tells me he can't be in a sexual mood "on command" just because I want to flirt. He also complains that he notices his age is causing him to be less up to sex in general, that he can't get an erection or can't keep an erection. But I don't see this at all when I'm with him. I've never noticed any problem with his stamina or ability to get or hold an erection. So, I'm a little confused. First, guys, can you really tell three days in advance whether or not you're going to want to have sex? And what's with the libido roller coaster? Any ideas what might be going on here? And how I can deal with it gently without making him feel pressured?