Please Help: Was This Cold Feet Prior To Marriage Or Did I Fall In Love With Someone Else?

I got engaged in Jan + we held a party for it in Feb. My fiance loves luxuries and invited lots of ppl including his best friend from law school, who is from england. From then, my fiance has invited this friend for weekends and dinners on a very regular basis. He is single, and is a very sweet man, who is able to express his emotions and is full of depth and character. My fiance is what I thought was the love of my life, he took me under his wing and has supported me through so much.Please Help: Was This Cold Feet Prior To Marriage Or Did I Fall In Love With Someone Else?
The wedding was going to take place in May. I have avoided his friend as much as possible, but he does and says the most wonderful things that I have heard in my life, so I started falling for him. Yesterday, I started feeling suffocated with my fiance and even though it was pouring outside, I ran outside without even a jacket. His friend was pulling into the driveway and saw me. He ran to me and I kissed him, and he did as well. It was magical. Today, I packed my bags and am leaving both. HELP.