I don't want to do significant other's washing
What happened when you did it before?
I tried to do some washing, but not all of my clothes were clean.
It's okay to not do all that for your SO. They can clean up after themselves. But you should both pitch in and help.
So I can go dirty and sniff sweaty clothes?
No, I don't think that is okay. But if washing clothes isn't your thing have SO do it and you pick up some other chores.