Is my guy friend embarrassed of me?

I've been his friend for about 2 years. Although he's not in any of my classes, we have been spending out lunchtime together in the library. However, recently, when there are a lot of people in the library, he just ignores me like he doesn't even know me...

I want to ask him if he's embarrassed by being seen with me, but I don't want to make him feel uncomfortable. And what if I do ask and the answer is 'yes'?!?!
Is my guy friend embarrassed of me?
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