Repeat this regularly:
'What an utter waste of space.
It's not me - it's him.
He is a manipulative, gaslighting coercive controller.
He has already got one woman pregnant and left her holding the baby.
He almost certainly didn't meet the current woman immedately after leaving me pregnant - he already had her lined up.
He will probably get her pregnant too.
He is now trying to control and manipulate me from a distance by trying to confuse and make me doubt myself.
There is something wrong with him - not me.
Thankfully I'm a mature woman with an income and experience as a mother, not an inexperienced dependant young girl.
He is just the sperm donor - and doesn't get to live in my head rent free.'
Keep telling yourself all this - it will take time if you're battling a mass of anger, shock, sadness, confusion, 'was-it-me?' guilt, fear and pregnancy hormones.
Restrict communications to one channel, formal email is best as you can keep all he writes as evidence.
Ignore all attempts to manipulate and DARVO you - keep everything factual and formal.
Don't get into text threads. They can get messy and spatty.
Remove any social media connections - the fewer channels he has to you the better.
You don't have to answer the phone.
Ring doorbell, in case he turns up.
Find out about child support. He has responsibilities, he will also probably have rights - and so do you. And your baby.