Bf got a friend name as y....?

my bf friend her name mel was texting my bf for advice.mel my bf ex gf but they are still friends.i don't mind them been friends i only saw the text message for 2 sec i didn't even read it properly but the name at the top read y mel.so i asked him and he said it was a joke as they use to go out and he hasn't changed it.i am a bit worryed cause what if shes flirting with him or hes flirting with her.me and my bf been going out 1 year now and i love him so much.im scared ill loose him.