Also, are you enjoying it as much as him? I have to wonder if maybe he is getting something more out of it than you? If it blows your socks off with enjoyment every time, then maybe you would be *wanting* to do it more often. If so, that's something you both need to work on. Like I said, men and women are just different at this anyway. Men have a huge sexual appetite, so there is going to have to be some compromise at some point, no matter what.
But at the same time, I hope he is pulling his weight and it's not one sided love making, if you know what I mean. You have to be enjoy a LOT or something isn't right. You don't have to want to do it more than say once a day. But that once a day should at least be something you really enjoy. Hopefully that is the case. If not, there are plenty of ways to fix that.
Doesn't sound too bad. It's really promising in the bit where you say, "whenever we are alone that's what he wants to do. a lot of times i am in the mood and we do,". But where it goes wrong is that he wants to do it again and you don't. There is nothing wrong with him wanting to do it again, it's perfectly normal, and us guys usually are pretty horny creatures. That's the way we are designed. We can have sex and then 20 minutes later we can have sex again. We are made to have sex over and over. Women are built differently.
So the first time you have sex is great! But then him wanting to have sex a second time, is perfectly normal, and you *not* wanting to have sex a second time is perfectly normal too. So then it's all just about compromise.
Some women just shut the men out completely and the men have to put up with it. That's not a very nice thing to do though. But you shouldn't just force yourself to do it either, and then feel bad about it.
You can still do it, even if you don't want to, and you shouldn't feel used at all. You should be doing it because you are doing it for your husband who you love, and you are doing it as a kind of gift to him, even you would prefer not to. That just a nice self less thing to do. But if you really don't want to do, then you shouldn't, and he needs to understand and appreciate that. And the only way he will understand and appreciate it, is if you tell him that you REALLY don't want to do it a second time, and you would rather just cuddle/sleep.
So you have to communicate.
It could be you, him, or both of you.
My best guess is him. What you are describing is some of the symptoms of sexual addiction. Some men get so addicted to the pleasure and release they get from sex, that they want it whenever they can. It becomes a type of drug. The escalation that you describe is also a symptom of sexual addiction.
Too much sex can make somone numb. Why do you think porn stars retire after about 5-7 years? Sometimes men think that after a woman has children, she will never want sex again. He might be cramming what he thinks is going to be 20 years of no sex into about a month!
Discuss this with your husband. Ask him why he wants sex all of the time. What's going on in his life?