He got another girl pregnant :(

I'm in such a bad way :( This is long, sorry.
My boyfriend who I'm head over heels in love with told me that he had a one night stand with another girl last October. It was a drunken thing that happened after we slept together for the first time but just before we were 'official'.
She recently got in contact to tell him she's 5/6 months pregnant and doesn't know if it's his or her ex boyfriends. She later said she did a test and it's definitely not her exes, although I'm not sure I believe her.
He says he wants nothing to do with her or the baby and that she's ruined his life and that he wants to be with me and work through this.
I don't know what to do. I love him so much but this is some Jerry Springer shit. We never even had one single argument before he dropped this bombshell. She's due in July and I know she's not lying about the pregnancy as I've seen pics of her 😓
What should I do? My heart wants to stay with him and hope it's not his and my head leave his ass ASAP. Any advice would be amazing.