Where do you get 9 months from?
Because he told you that's how long it lasted and when it finished?
Why would you believe anything he tells you after he's committed the ultimate act of deception and only came clean after you confronted him with indisputable evidence?
Stop trusting, start digging.
And no, in my opinion you can never, ever trust him again but that doesn't mean you can't save the marriage, it just won't be what it could have been if he didn't mess everything up.
Because he told you that's how long it lasted and when it finished?
Why would you believe anything he tells you after he's committed the ultimate act of deception and only came clean after you confronted him with indisputable evidence?
Stop trusting, start digging.
And no, in my opinion you can never, ever trust him again but that doesn't mean you can't save the marriage, it just won't be what it could have been if he didn't mess everything up.