Non-exclusive but Jealous

I have been casually dating a guy for a couple months now, and we aren't exclusive (since we're still casually dating). He admitted that he had a one night stand a couple weeks ago.

He didn't do anything wrong, but I have been cheated on in the past and am extremely hurt by this. I keep going back to the fact that he didn't do anything wrong since we aren't in a relationship.

I just wanted to know if you would consider this a deal breaker in a period where you're still trying to figure out if you want a relationship with the person.
Non-exclusive but Jealous
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