what does "Mwen mwen" mean, i thought it "I" in creole. both of them together mean what?

I think you're talking about mwen menm, not mwen mwen. Am I right?
You've probably seen it in phrases such as:
Se mwen menm - It's me.
mwen menm avèk li - me and him/her or He/she and I
Kanta pou mwen menm... → As for me ...
etc...

Mwen menm can translate I or me.  See this link: Mwen menm
Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words