The word has many meanings.
The main use is a synonym for sleep deprived, as if you got only six hours of sleep.
It can also be a word to describe just how awesome something is, or just how sad/annoying something was, it all depends on how you interpret it.
“Yo jude i hardly slept last night i just feel willy pillowed” (tired)
“that party was so willy pillowed man” (lit)
“bro my gran just died i feel willy pillowed” (sad)