Call me Duvet cover

My metaphor is a duvet cover
To change me is a bitch
It only comes a problem
when I cause you to itch

Can never find my corners
I tend to make you shout
I'm lumpy in the middle
I'm always inside out

You'll never smooth me over
I always tend to crease
However much you iron
My crumples will increase

When you think its over
There will be another fight
For my buttons are all missing
and fasteners are shite