So having sex when you don't want to have sex can give people the same psychological effects as SA survivors. I'm not saying that you have to be leaping for joy to have sex every time - you can feel like, 'oh I'm not sure about x thing but lets try it', 'I'm a bit tired but feel ok with this', or even, 'this is a bit boring but it makes me feel happy to see my partner happy'. When it becomes a problem is when you genuinely don't want to do something, and you still do it anyway. For example, when you feel really exhausted, or stressed, or you just really don't enjoy a specific sexual move.
It can technically actually be assault, depending on whether or not your partner believes you to be consenting. For example, you might not want to have sex, but pretend to want to have sex because you hate confrontation. Or you might say, 'yeah sure, I'm a bit tired but this sounds good to me', so telling them that while you aren't massively enthusiastic you're still good with what's going on. This is what I used to do, and while it's a crap situation, it's not SA because my sexual partner genuinely believed I was consenting. However, it still really fucked me up - I'm an assault victim so when I had sex (which I didn't want to have) I was reliving my assault, which traumatised me further.
However, if you've said to your partner, 'I'm not really feeling like sex' and they keep pressuring you ('why not', 'you're a horrible partner for not doing this for me', 'I deserve this', 'come on, it will only take 5 minutes'), then it is actually sexual assault because your sexual partner KNOWS you don't want to have sex, and you're only having sex b/c they keep pressuring you. Basically, it's SA if you've communicated that you don't want to have sex and they keep pushing you. In your case, I'm not saying this for a fact, but if he's unkind to you/sulky/rude to you if you don't sleep with him, this could technically count as sexual coercion (forcing someone into sex through pressure - in this case, the pressure of his negative reaction) depending on how intense his reaction is. It might be worth looking into this?
It's really good that you aren't experiencing any negative symptoms, I'm really glad about that. I still don't think it's a healthy situation to be in, for you. You should enjoy sex as well, and you should feel like you're able to say 'no' without any negative consequence. I really don't want to cause offence or suggest that your partner is abusive, and it could genuinely just be that you aren't communicating. But the phrase 'the household is happier' if you have sex with him did set off alarm bells in my head, so I felt I should say something.