positive opk 4 days before period !!!!!

So I had 1 opk left so I used it just messing about really well it come back positive?????
4days till AF arrives 
Has this ever happened to anyone I'm 11dpo 
Cm is creamy could I be ovulating or could it be I never ovulated when I thought I did (but I did get all the signs)
Really confused any advice would be helpful x