My girlfriend and I have been dating for many years. My girlfriend has always had plenty of guy friends and we have often discussed having threesomes but have never acted upon it.

Last summer my girlfriend returned to her home town by herself for a week or so. Many of her girl friends were away at the time so she spent much of the week with her closest guy friend. He is our age, very sporty and athletic (my gf jokes about his abs occasionally). They went out for dinner on some occasions and even went to a batting cage one evening. At the time I didn’t actually realise that it was just the two of them but I am quite late back so nothing came of it.

After a week, I also flew over to visit and join my gf. On the first night we spent the evening with just myself, my gf and her guy friend. I noticed that evening that my gf and the guy were getting along really well. They were joking and touching each other. At one point they even started tickling eachother ‘jokingly’ which I thought was interesting. The behaviour did seem a bit flirty but I didn’t quite put two and two together.

That evening when we came home. My girlfriend said she had something to tell me. She said that she’s been having sexual thoughts about this guy all week. And they’ve been subtly flirting with each other and going on pseudo dates (i.e. to the batting cage).

Upon hearing this, I was speechless. But I felt really strange. On one hand a part of me was humiliated. But at the same time, I was overwhelmingly horny. So much so, that I had a raging boner. I quickly ran to the toilet and had to masturbate to the thought of my girlfriend and her friend fucking. I came so quickly. I returned and told my girlfriend that all was okay and I forgave her. We had insanely good sex that night.

All I can think about now is her and her best friend fucking. But my girlfriend has been super apologetic about the ordeal. She feels really bad - but part of me wants it to continue. Part of me wants her to pursue this guy, and keep flirting.

What do you guys think - am I weird for feeling like this? Should I tell my girlfriend how I feel?