"We tried only having sex on weekends, but I'm still so tired and have turned him down anyway. "
The more you do this, the more likely you will lose him some day. Is that what you want? While you may be very tired, you still have to focus on your relationship if you want to have it in the future.
Is he helping you or anyone helping you with kids and home? Are you doing too much? Trying to have a perfect home? When do you try to have sex, is it at the end of the day when your energy is the lowest or you have you thought about trying first thing in the morning, maybe before the kids are awake? Excess energy is needed for sex so trying at the end of the day usually isn't the greatest thing to do, even though it seems like the most natural time to have it, when you go to bed.
" I mean last night was great, but now I feel like I don't need any for a while. I guess I'm just going to have to force myself to do it when I don't want to? "
Forcing yourself isn't necessarily good either. Yes, the experts say "Just do it" but the assumption is that you can find something enjoyable from the act of sex or making loving once you get started. While your husband may want 4-5 times a week, he has to compromise also. Two times a week seems like a good compromise and it sounded like he compromised to weekends only for you. Now you have to step up and meet the compromise. If you don't, you put your relationship in jepordy.
So do you enjoy sex once it gets started? Maybe the touching, kissing, caressing, etc? Does he expect you to have an orgasm all the time or just try to enjoy being with him? Can you look for the positive in the act and want this connection will do for your marriage?
Is he helping you or anyone helping you with kids and home? Are you doing too much? Trying to have a perfect home? When do you try to have sex, is it at the end of the day when your energy is the lowest or you have you thought about trying first thing in the morning, maybe before the kids are awake?
My DH does not help me much around the house.
"We have 3 young kids, including a 9 month old, so I have to wait till they go to bed to get alot of stuff done. "
So here is one place the hubby could help out so you can do your thing while he takes of the kids. Explain to him that sex requires energy. More so for you as you have a 9 month and no doubt your body isn't back to it's natural sex yet. If you breast feed, that can take away from your sex drive also. So if you want to have sex, you need to find the energy. Here is how he can help. He takes care of the kids and you do whatever chores you want to get done.
"And of course we have to wait till they are asleep to even think about sex. And we just don't like morning sex, it's not our thing. "
Well here is where you both can make 'temporary' adjustments. Kids force us to do those type of things if you want the relationship to survive and thrive. Yes the morning sex may not be your thing but it also when you both have the most energy per scientific studies. Maybe one day out of the weekend, you both can learn to move out your comfort zones and make it your thing until the kids get older. You have to adapt, just temporarily, if you want your relationship to survive. Kids grow and leave. You get the house back to yourselves one day again and do whatever wherever want at the point. Mean time, you have to learn to adapt to survive. Basic nature thing. :-)
As for waiting for the kids to go to sleep, you'll need to learn to expand your comfort zone on this one over time. As they get older, they stay up later, like 1 or 2 AM in the morning as teenagers if there is no school or work the next day. Are you going to put your sex life completely on hold? No sex in morning, no sex because the kids are awake? You aren't going to find any time left for physical intimacy.
"Usually I do enjoy sex once it's started, but that's only if he takes the time to stimulate me. He doesn't expect me to have an orgasm every time, but I do. It really bothers me for him to just have sex with me, and I'm not enjoying it. I feel like he should want me to enjoy it too."
Most of the time what you say should apply. He should want you to enjoy it but how you enjoy may be different than how he enjoys it. Which is fine as, again, there is enjoyment for both. Have you had discussions with him about what your needs are when you have sex? That it is an act for two people, just not one?
" We had sex last night eventhough I wasn't in the mood, so that's two nights in a row for us, something that hasn't happened in a long time. "
Well I hope it ended up enjoyable for you for both nights.
"So when they are up, no we can't have sex. Now, as they get older that is different as they will not have to be watched."
Sounds to me like you know how to make things work in ways to keep the couple going.
"But I am pretty tired, and sore actually. I think I need a break for a day. "
Your current agreement with your current family situation was twice a week I believe so you're tired, take a few nights off if you need it to try to recharge and/or get other things done. You're trying to find a balance that keeps both you and him happy, just not him. Lovingly remind hubby if you need to.