Fixing grass lawn

Hi .. can anyone tell me how to fix my garden lawn. I moved in and tried to thicken the back lawn by seeding it .. this didn't work .. I then put a layer of compost on it and reseeded .. the grass grew but the area is still very bogey and still thin. I have fed it .. aeriated it .. and cut the grass that did grow .. but still very wet and thin. Tried to put thin amount of sand through it to help drainage but still very wet underfoot ... Any suggestions? Thank you