i constantly hear my dad and his gf having sex :/?

Why don't you discreetly tell his gf? Maybe THEN, she will listen and be "quieter"'. good luck. Peace.

If you think it will be too awkward to bring up, the next time you hear them having sex put on music and turn it up fairly loud. They will know when they hear it that they are being too loud and you can hear them and you have a problem with it. If it's later at night when you are trying to sleep, you could knock on his door and play dumb. Tell him you don't know what he's doing but you are trying to sleep and ask him to please keep it down. His girlfriend will probably be embaressed and stop doing it when you guys are home, or close enough in the house that you can hear. I know it seems like it will be awkward but I would honestly suggest just bringing it up one day. You could say something like, "I know this is your house and you are allowed to do whatever you want but the walls are pretty thin and the things i hear when your girlfriend are over are making me and (sisters name) uncomfortable. I didn't want to bring it up but it's really been bugging us." It will be fine to bring it up. If you don't say anything, nothing is going to change. You don't deserve to feel this way in your house. Your dad will understand.

Haha Okay this happened to me too! Just wait until the next time you see them and tell tem to be quieter and that you heard everything. It will def embarrass them!!! And the will stop

Next time just go knock on the door and say daddy are you awake I think I heard a noise in the living/kitchen.

Maybe try writing it in a letter from both you and your sister to avoid face to face or have you tried ear plugs.

ok if you hear them again then tell one of your family members or your mother if you have one . you could tell him to stop or else youll leave and go to a family members house

Bang on the door. Problem solved.

Put on music to drown it out.

Tell your dad to get of the B1TCH!