Boys will be Boys

My boyfriend and I have the same friends, he is obviously more close to them considering the fact that they are mostly guys but occasionally they'll talk to me instead. Just the other day his best friend was asking me about advice on girls and such. He was telling me how he never really talks to my boy friend anymore how it's like whenever he gets a chance he just doesn't know what to say and he feels as if he is losing a friend. I agree, lately my boy friend has been more susceptible to his other friend.
I understand that they are slightly different for example my boy friend is madly in love and his best friend believes in having sex with as many women as possible before he dies. I'm not entirely sure what is making them distant but it scares me because it proves my point. I'm always afraid that Liam or I will change and fall out of love. Liam has changed and is no longer best friends with his best friend. I hate change.