Why Did I Do This?

hey so i was at this place with janet from work we kinda flirt a lot but nothing happened til last night . she said let s go to her place and i did it made sense in the moment but now im all over the place thinking why ? is it just because of the thrill or am i actually feeling something for her? my partner knows its an open rel ship but this feels different somehow not sure if thats a good thing. i keep trying to figure out what exactly i want from this but cant put my finger on it.