I think I am falling for my fwb

I even don't know where to start...I am engaged to my fiance(long distance relationship )for almost an year now ,dated for almost 8yrs now...but there seems to be no communication on when his people will officiate and come meet my people that event just keeps on getting postponed....Anyway that's not what I am here to talk about...I met someone else and in an entanglement.The sex and everything else is sooo intense, we have this connection that I have never had with someone else,we understand each other, same career, similar goals in life and even if he is slightly younger than me we still vyb and have an amazing entanglement.Today he told me that his girlfriend is going over to his place and my jaw dropped...I felt this intense feeling and am just not at peace..it's wrong to feel this way because he is not mine but I just keep thinking about is dating exclusively.....I really do like him alot but am I really falling for him or it's just that I am dickmatized?...I have never cheated on my fiance before and this is the first time and it feels soo good being with my fwb....on the other hand my fiance has cheated on me countless times.....should I let him go and pursue my fwb?