I have been friends with this woman for many years and we had a friends with benefits arrangement going on for the past month and a half, and i stopped it due to the increased time spent as well as the heft of a relationship when it was not the case (i.e lots of time spent with each other, cancelling plans, etc). This was agreed upon beforehand as a friends with benefits which would cancel if either one of us slept with someone else. The longer time went on, the more i felt unhappy, which is why i decided for it to end. I understand now that she wanted a relationship and wanted to go further but i simply could not do it to simply because i did not feel the same way. Now i feel bad while she does not mind, as she thinks that i'm overthinking it all. I am young and this was kind of my closest loving situation i have had, but i have never felt so bad due to me thinking i was just using her when that was not the case.

TLDR: i stopped a friends with benefits because i was unhappy and because she wanted a relationship but i feel terrible.

Edit: wow did not expect this many comments! I genuinely appreciate all the feedback and opinions expressed, I am quite young and it was probably a bit stupid of me to be so naive at some point but sex does really complicate things, jealousy was involved and that wasn't on my end, and that was another point that stopped it on my end. Fwb should be just that, but lessons have been learned and that's what matters.