I've had a partner I've been seeing for a number of months, sex has been great and we enjoy a lot of laughs. Been seeing them regularly. I have been feeling a lot of NRE and attraction. We had a threesome recently and it was fun, safe and I'm glad I did it, but over the past few days I have had this huge shift in my feelings toward my partner. Now, I almost can't even imagine having sex with them again or engaging in any type of romance, despite the fact I know they want this with me and feelings aren't different.

This shift in my feelings happened so fast that I don't even know how to make sense of it. Its like there are so many red/yellow flags I'm seeing now in our relationship that I was totally blinded to before. I feel like these things are dealbreakers and somehow I totally missed them while in the throes of NRE.

I feel like I need to tell my partner this but I also wonder what point it serves? We both have primary partners and this is a secondary relationship for both of us, so maybe I can just ask to be friends and not be romantic? Do I owe an explanation of why my feelings changed? Can anyone give me advice on how to navigate this huge dropoff in my attraction/desire for my partner?