Listening to my boyfriend talking in the shower

My boyfriend was taking a shower and I went in to pee. The door was already cracked open so ig he didn't hear me walk in. As I'm in the bathroom I hear him talking. I listen and he's umm. Having a whole conversation with himself. I just stand there fir like 5 minutes and the slowly pull the curtain back. He looks shocked and I'm like "You good?" And he says "How long have you been standing there". I said "Long enough to know you not only talk to yourself... But respond to yourself". He looks humiliated and pulls the curtains back and told me to go away.