Am I an embarrassment???

We have almost been dating for 5 months. I changed my social media names to show I was in a relationship ages ago. I asked him if he was ever going to put the fact that he was in a relationship anywhere at anytime (not my name specifically if he doesn't want to just "taken" or something). He wrote "her" once then took it down so I asked why and his response was he didn't want any of his ex girlfriends messaging me and telling me about him that would make me break up with him? Is that a legitimate excuse? I feel like he's embarrassed by me, due to our age gap of him being 15 years older than me. Thoughts?