It’s weird that you didn’t instantly recognize it wasn’t your boyfriend and you seem to be doing a lot of deflecting. The TLDR is worded so strangely too, the stranger got kissed by you, not you kissed a stranger. Shifting blame.

Did you want to kiss your coworker and now you feel bad about it?

Yeah, no, this doesn't happen outside of sitcoms. I have pretty piss-poor facial recognition, but even I would be able to recognize that someone was a mild acquaintance and not my wife.

Where was your boyfriend?

Why is your boyfriend's coworker showing up at your place?

Did your boyfriend not come to dinner that night?

Did the coworker join you for dinner?

None of this makes sense.

This is 100% not real at all u/freemiumsucks

Half an hour ago it was a stranger...

Only thing missing is the boyfriend showing up Behind the coworker after the kiss saying "Honey hope you don't mind I invinted my coworker for din..."