What do you think of me telling my parents that I can't stay with them until they clean the house?
Are you telling them that because messes bother you?
Yes, it's unbearable to live in this dump.
Even though they won't be happy about it, it is good to let them know the truth. It could be a health hazard if they don't clean and being honest with them might make them clean.
It's more important to have pride than clean. Besides I hate this house.
Being honest with your parents is okay, as long as you do so respectfully. It would be great if you can pitch in and help them out also.