I always thought it was about suicide and drug abuse. Hes tried many ways to kill himself, (shes a freak in the sheets) and when someone asks (play it cool) as to not reveal himself. Also inspiring the line (try to listen but her whispers make my ears hurt). Everyone telling him to stop is so much its become overwhelming. Hes having sex with a ghost meaning hes been in the situation so long and tried so many times its like hes having sex with it. idk, I tend to overlook things