How to prove that a language is not context-free using pumping lemma I'm trying to prove that that language isn't a context free:  

$ L = \{ w11w \mid w\in \Sigma^* = \{0,1\}\}$

I succeed to prove that $L = ww$ isn't context free, but not the language above.   What am I doing wrong?
Here is the simplest way. Suppose that your language were context-free, and consider its intersection with $0^*(10)^*110^*(10)^*$. Applying further simple manipulations, you reach the language $\{a^nb^mc^nb^m : n,m \geq 0\}$, which is known not to be context-free.

If you insist on using the pumping lemma, perhaps you can get inspiration from this argument.