I've been seeing G for about a year now and have had several short term dating episodes with other people during that. One of them is R, who I maintained a loose friendship with after we stopped sleeping with each other. I'm also currently dating T, who is of no further relevance to this post, just wanted to mention it. It never was a problem for G and she also hooked up a couple of times with others. We don't live together and see each other around once per week. Our relationship status is a bit undefined since I feel a lot of affection and appreciation towards her but not really a feeling of big romantic love. We agree though that it is no problem of seeing others and developing emotional bonds with them.

Yesterday (Saturday) I came back from a week long vacation with some friends. G had taken care of my plants during this week. Since my train would arrive very late and the journey take a long time, we decided to not meet Saturday evening but rather Monday evening so I have some time for me alone after constantly being around my friends for a week.

During the train ride I chat with R about her chaotic dating life which eventually leads to some more spicy messages and her spontaneously inviting me over shortly before my train arrives. I felt way less tired than I had expected so I accepted and headed with my luggage to R's place instead of my own. We have sex and I spend the night since it's already past 3am then.

Today (Sunday) I come home around noon and find a handwritten note with a short original love poem by G next to my bed, which she placed there while watering my plants. I only looked into my bedroom because G messaged me about if I had discovered her note. Nobody has ever written me a poem before and I feel so loved and appreciated right now.

But I also feel so ashamed and guilty for having made plans with G only for Monday because I thought I needed time to relax and then go out and sleep with somebody else the minute I come back. In the morning it still was a minor lingering feeling, but finding that poem triggered some major feeling of "I don't treat G the way she deserves, I should have spent my first night back either alone or with her" and I feel like a terribly ungrateful ass right now. Objectively speaking I don't think did anything that violated any boundaries we set but it suddenly nontheless feels like I did something very unethical.

I told G about the situation and get response was that she needs some time to process this info, so she isn't entirely unaffected by it. I'm confused by the intensity of my own shameful feelings (big enough to make my first post on this sub). I never had those before after sleeping with others, so I think there's some entanglement of different issues going on. Can somebody help me untangle it?