Really well said, I appreciate the message.
The word "love" kind of freaks me out though. Maybe I am a bit distant, but I would never profess to have met the love of my life, or give someone that title after knowing them for such a short duration of time. I almost feel like we're plunging the depths of subjectivity with that ideal.
Given this response... i think what is bothering your boyfriend is that something about the encounter made it clear to him that you really do not "love" him in any way that is deep or special.
That he has no more a hold on you than any other man who might be fun in the sack.
In other words, you did not make him feel that this was something you and he were 'sharing', but rather that he was just another dick at the orgy.
That is a real pity... Its okay, I guess, at 25 to be footloose and holding your heart in reserve... having sex for fun and laughs...
but you should be mature enough to realize that most people want something deeper out of sex and that they do not call it "making love" for nothing.
And I would warn you that you can inure yourself to the idea of being emotionally aloof... of not committing, of not investing your heart in anything. It can become a habit, and from there, a handicap.
Perhaps you were very seriously hurt, early on, and felt betrayed or abandoned in some situation wherein your heart was invested... and you are coping with that injury by armoring yourself to any further injury... practicing sex without love the way a snake handler takes small doses of snake venom to build resistance...
But loveless sex is no different than masturbation... there is more feeling in playing checkers with one you really care about than in wild sex with a person who means little to you.
Your boyfriend, in seeing you with another, saw that he was only temporary... and he is in mourning for something he wanted to be much much more.
Time is wasting. Life trickling thru your fingers... a third of yours, already gone. Isn't it about time you took a break from sport fucking and looked at the question of real love, real commitment and a real relationship?
Or do you imagine that you will find the love of your life in an experimental sex session with some other couple?
On the one hand you strike me as a beautiful, hot, and sexually daring woman.
And on the other, you seem to be sleepwalking thru the lives of the men with whom you take up.
I sincerely hope you find, someday, a man whose touch can make you wish to touch no other.