Why would a guy I'm exclusive with leave me out of his bday plans?

I've been seeing this guy for 3 months, last month when I asked him where this was going he told me he's not seeing anyone else and wants this to be exclusive.

It's been a month since then. It was his birthday recently and he told me about a party he was doing but he didn't invite me to it. He also didn't invite me to his bday dinner.

What does this mean?

Why would a guy I'm exclusive with leave me out of his bday plans?
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