How do I get over my insecurities?

I’ve been seeing this guy casually for a month but we’ve been pretty hot and heavy.
He just went on vacation and my mind is running wild. I’m afraid he’s going to get intimate with someone hot on vacation. if that was the case it would ruin things for me but on other hand he wouldn’t be in the wrong. We aren’t committed and he’s an attractive single man.
I feel like I should wish him a good vacation mean it and get over myself.
Regardless I’m struggling ! Am I crazy for feeling insecure?
How do I get over my insecurities?
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