This is a rough one because basically when it comes down to it, you ARE rejecting him. Men want sex frequently (well, a lot do) and it's hard to always be up for that. Try whenever you can though because for some men, this is how they feel close to you. What you can try . . . tell him that "oh my gosh, I'm so tired and I was looking forward to being with you (as in doing it) but you don't have an ounce of energy. Could HE make time for you tomorrow?" Try to soften it that way. Not, no. I'm tired, I don't want to have sex. But rather, i'm so disappointed in how tired I am and can't wait to get some of you later . . . something like that. Do you think he'd respond better to that?
Lots of couples go through this and when it is not in the heat of the moment too, you can try to talk to him about it. Letting him know it's not a reflection of him. He may be a more sexual guy than you and it's good to know that at this point in the relationship.
You shouldn't feel guilty, by the way. You are entitled to have time in which you aren't in the mood. good luck
marriage is about compromise - a compromise would be the middle ground of him wanting it everyday to you wanting it 3 x a week (let's say). There are many things at play in an adult relationship - work kids etc. I remember when i was working 12 hours shifts, i'd have to shower after work and fall into bed. My husband expected sex whenever he wanted. If we did do that, it would mean that i would need another bath in the morning before work, i'd have to get up an extra half hour to get everything done. Sometimes it takes a conversation about the realities of one's expectations. If you're not able to have a loving conversation about what it also important to you, is this the right man for you? *i'd be asking myself. I would absolutely not stay involved with a man that was in any way aggressive about sex after i've made it clear it was not a comfortable time for me. The operative word being man and not boy. A boy , if he really likes chocolate , might want to eat it everyday, all day. If he's been taught that you can't always get what you want, that all or nothing is not good for a person, he would grow into a man that will understand compromise. If he was always given into as a child, he might not be able to understand compromise. Depending on what type of man your bf was nurtured to be, is how you can get through to him as an adult. In other words, a man can learn and grow to compromise, even if he has not been taught to, it's just that much harder than the obvious ideal of having a loving man that understands other points of view and have empathy for the concerns of others.