Yes, I have.
Its pretty heart wrenching. My situation was a bit different though. So I was in a relationship for a few years and yes "cheated" on my then partner with an acquaintance in which I had very deep emotions I thought and still think was love. Unfortunately I didn't get to make the choice and in saying that maybe that's a good thing and things just panned out the way they were supposed too. The guy I was with found out and blew his top...the guy I was seeing didn't want to see me and ended it and to my sheer shock my partner still wanted to be with me.
This is all so esay to write but there is a lot more to it.
I suffered for a long time for falling in love with someone while I was still in love with someone else. All the feelings, Anger, guilt, shame, sad, lonely etc...
I really can't explain the feeling of one's heart completely breaking from losing someone while still holding onto to another love that's alive and wanting you .
My advice in this situation would be...if you do fall in love with 2 people..maybe be the one to step back and let people come forward and tell you that they love you and if you can honestly say you feel the same then say it back, but don't tell 2 people you love them, I think that causes too much confusion even if that is what you feel in your heart of hearts.