I understand your pain, confusion and anger.
The truth is that: you were not the one for him; he did not want to commit to you. He has now found someone that he wants to commit to.
That is hurtful to you because:
You were committed to him
You viewed him as the one you wanted to spend your life with, acted accordingly and assumed the same
He effectively lied to you because he didn't tell you the truth
This means that he was essentially using you as a "comfort" until the woman that he actually felt able to commit to came along
He didn't make you aware of this decision so he effectively wasted your time, as he knew that you actually were all in
It makes you wonder what she has that you don't etc, which are insecurities or concerns that you probably never had before. Now you find yourself comparing yourself to some random woman which you would not have done before, etc.
There is really nothing more to say other than he treated you extremely unkindly. He is a selfish, self serving individual. He treated you badly. There is no real way to sugar coat it. A man with more integrity, upon realising that you were fully invested when he was not, would have stepped back. Anecdotally speaking, in my experience a lot of men don't have that level of integrity.
You are not wrong to be hurt, confused or angry.
What you can do is focus on yourself now. Cut him off completely - stone dead. Do not allow him any access to your life, and do not give yourself any access to his (social media, etc). Cut him out of your life stone cold - you don't need to see or know or hear about his new relationship, how his life is panning out, what could have been or would have been - stone cold cut off. This person should now be dead to you.
Then. Focus on your own life. What YOU want. Who YOU are. Celebrate yourself and the wonderful qualities you no doubt have. Review the past 9 years without rose-tinted glasses - identify the things you compromised on, things that annoyed you that you accepted, the things that were not as good as you thought they were, the things you ignored, the things you wished for that didn't happen etc
Resolve never to sell yourself short again.
Be intentional about what you want to do next. Do some stuff for yourself that has nothing to do with relationships - just things that make you happy. Take this time to be happy, to love yourself, treat yourself, know yourself and regain hope for yourself.
Your happiness is NOT tied to this timewaster. You are more than this 9 year relationship so find out what this looks like in practicality.
My mum always used to tell me "every pot has it's lid". This was not your lid. That is ok. Re-group and gather yourself. And then, only then, think about finding "your lid".
I am sorry for your hurt. It's horrible.
Sending you a hug. I am not sure why this is always caveated as UnMumsnetty but am sending you a big one.