Try switching types of creatine. Monohydrate works best for me, CEE never did much.
I gave ~500g of CEE to my buddy, who was using various other creatines. He said it feels totally different but in a good way. His lifts are up, he doesn't get as sore, etc.
*shrugs* Different strokes for different folks.
And to answer your question, I have never tried nor even read anything on injectable creatine. Sorry.