I have no idea if I'm his girlfriend?

I've been on 5 great dates with this great guy. We have talked everyday and become very comfortable. Our 5th date (4th of July) I was joking with him and said "are you sure you don't have a secret girlfriend you're so nice and cute it doesn't make sense" and he said "you're my secret girlfriend". It was a casual conversation so I'm not sure if he actually made me his girlfriend or not? He does want me to meet his friends and has told them about me so I know the "secret" comment was just him trying to connect conversation. But I'm not sure what to think, am I his girlfriend?
I have no idea if I'm his girlfriend?
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