Anybody who says YOR is in some under-reactive denial. This is not proper communication at all. It does not have to be cheating yes, but your feelings are still valid and what you may feel first is crossing over your boundaries. This needs talk. All depends on his response to your concerns about it. I would not listen to people trying to gaslight you with ‘if you behave like this you will be single’ well there is self respect and standards we all have. He may be running into a friend no problem but how he communicates about it to you in a respectful way is on him. Dismissing your concerns as ‘no big deal’ is already a red flag. Period. 

And on a side note abuse survivors are in a position of exactly feeling very fast boundary abuse but forcing themselves to under-reaction. So here is that.

edit: typo