Does my coworker have a crush on me or am I making it up in my head?

~3 Months ago my coworker started staring at me. He whistled a song every time he walked by me and once he had realized I was at work, he would keep popping up in my areas.
But…he also has not talked to me once. And he came in today on his day off with 2 girls to go grocery shopping. So I think that’s a bad sign.
Am I reading into this too much? I feel kinda crazy

Does my coworker have a crush on me or am I making it up in my head?
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