What to do?

Last night on the phone, my boyfriend of a month told me he thinks he’s still in love with his ex. 😞 I didn’t see it coming. This past month has been amazing. I thought we were having a great time. I’m 18 and he’s 23. He just said he thinks he still in love with her, asked if I was okay and got off the phone. What am I supposed to do with that? I cried myself to sleep last night.