I know we agree to an open relationship (kind of) but did he had to do this?

My boyfriend of 3 years and I have been having issues and arguing for several months. By mid July we agreed to have a kind of open relationship.

I didn't even try to hide the dating site. I already told him in advance what I would do so no point in hiding. I purposely logged in and put my profile. I did all that in his face and he didn't seem to mind. I went on two dates to the movies. However, we didn't do anything beyond that. I can't jump into bed that fast.

However, while I was working I learned my boyfriend did it with the girl he knows I hate the most. He had the nerves to feed her my meals too. Anyone but her and why feed her my food? Did he had to do this? At least I didn't go on dates with guys he knows and didn't do what he did.

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He could've chosen any girl (there are so many) and he had to select one I know and hate the most since my HS years.
I know we agree to an open relationship (kind of) but did he had to do this?
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