FWB just told me they found someone and are currently starting a relationship. Am sad, wut do?

So this guy I have been in a friends with benefits relationship since the beginning of September just told me on Monday that he was "seeing someone so ya.." in that exact way, hes not a very enthusiastic texter but I only replied "Ok" he hit me up 8 days before that asking to come over to fuck but I had to work in the morning so I said another day which he was fine with. Im so distraught about this and I didn't think I would be but he was so nice and cuddley, very romantic, also everything I like in a guy physically. We talked a lot he has a great personality, the guy hes dating he only started talking to 3 weeks ago. The part that fucked me up the most was that when I asked if we could still be friends he said of course, then said "Im just saying im in a relationship now and I don't cheat when I'm committed" which makes sense but the next text after said "If things don't work out you'll be my first call." I don't want to be some piece of ass for him but I don't know how he even feels about me so basically i'm asking for advice on what I should do, I think I like him but I fear rejection and I don't want to make things awkward or end things as a friend because of my jealousy... wut do reddit :( :( :(