Most Helpful Guy
If you read the 3 previous posts, I do have to agree that this is possible. The other plausible option is that he is seeing more than 1 girl and obviously wants to hide this fact. I'm sure either of these possibilities are hurtful to you and I'm sorry, but I don't really see many other reasons for a guy telling you that. My best advice would be to find some else who does not mind people knowing that you are his girlfriend.