I can understand why you are confused about the situation. You mentioned that you’re afraid that your friend will soon have a breakdown. It’s curious to me that you seem more concerned about him that about your own well-being. We have no idea what’s going on in your friend’s mind, so at this point, all I have to work with is how you’re going to handle this.
While your friend expressed that he had feelings for you during that brief window of time, his choice to marry his fiance speaks pretty clearly about what he wants in the long run. I can only imagine how it is extremely awkward at work to have this intimate exchange at the bachelor party and then not process the experience and come to some understanding of what it means.
I think it’s really important for you to get clear on what you want to happen next. What do you want in order to get off of the “emotional roller coaster”? What would your relationship with him look like right now? Once you’ve clarified what you want to have happen, I think it would be helpful to have a brief conversation with your friend about the incident, come to an understanding about what it means to your friendship, and decide together how you’d like things to go from here.
If your friend is unwilling to talk with you, or if you talk and continue to feel confused and distressed, I recommend that you seek some psychotherapy to help you work through your emotions. Thanks for writing in and I wish you the best in this difficult situation.
Take good care of yourself!