I presume j'suis is slang for je suis. That much for the lexical formation of this "expression," which has been detailed elsewhere. However, I don't know the contexts in which it can be used. Is it ...
I'm French study beginner, so I don't have so much knowledge about French but I'm trying to read a book, in which I found the sentence “c'est pas d'sa faute”. What does “d'sa” mean in this sentence ...