I don't normally say this but, thank you for sharing <3 It can't have been easy, and while you might not have been very self-aware then, it takes a lot of awareness to be able to speak out about stories where (like here) you were "the bad guy". Though I don't think you were. It doesn't sound like you set out to break this man's heart which would've indeed been cruel. You fell in love with someone else - a very important and valued someone, as it turned out. To act any differently would've been wrong, I think :)
I carry guilt a lot - it's kinda a woman's thing isn't it? I don't think men in the same situation would have dwelt as much.