Is this common?

My boyfriend and I have had Vanilla sex (can’t even moan loud) these past two times because all the kids were in the house (they’re normally working), so I’m wondering if it’s normal to feel “off” or “down” because we haven’t been able to have sex like we normally do? Does this happen or is it in my imagination? I just can’t shake this negativity off and I don’t know if that might be a reason. Nothing’s happened at work or family to make me feel unhappy.