Hi, this is such a tough thing to go through, but I hope you're feeling like there are so many of us who go through/have gone through this.
My advice is to not try to make yourself feel something you don't. Think of a time when you weren't able to sleep (I know, bad timing!). You lay there thinking that you MUST sleep and it makes it worse. Same with sex. Thinking you should want it, it should be great, etc., just stresses you out even more.
Know that it is normal after kids to have sex drive change and diminish. Thinking of it as an obligation is not a terrible thing. You went from being kid free and energetic to kid full and tired. So for the moment, you are maybe having sex because you love your husband and don't want to deprive him. Simple as that. It still comes from a place of love, just with a different look. I think if you tell yourself (and maybe him) that you feel like once or twice a week is what you can handle right now, just go with that. Yes, it may seem weird to schedule it, but if that's what it takes- that's what it takes. This way the pressure is off, and hopefully in time the feelings will return and it will get better. Husbands have a hard time with this, I know mine felt like he was forcing me to do something I didn't want to do. I finally got him to understand that I wanted to do it for him because I love him, and it wasn't awful, I just would choose sleep if I could! Once the pressure was off, we lived with that for a while, and things are now better.
Good luck, and don't put so much pressure on yourself!!