Actually I have this question for long time. As I started to use contracted words like I've , it's, you're (verb with subject), and due to habit of shorting verb+not like haven't, isn't etc, eventually I came to write words that are contracted twice e.g I'ven't, it'sn't, you'ren't etc.
But I suspect about correctness of it since that I've never found such twice contraction in a sentence. So, finally I has come to ask: Is it ok to contract and combine more than one words simultaneously?
I mean combining effects of
I've + not &
I + haven't to
I'ven't! and similar possible word contractions.