How about, "Dude lay off, I have a boyfriend."
best friends are rare and precious ...if you start dating your best friend then you both will lose your best friend :)
Quit the 90210 bullshit and make up your mind now. You either want to be with your bf or your best friend. Then.... do it. Stick to it. And don't complain if it turns out wrong.
Well since your boyfriend's already your boyfriend and like you said you love him more.
Just choose who you'd rather be with. If you're boyfriend's loyal and good, I suggest you try staying with him and tell your best friend you'll get back to them.
Whoever you don't choose, just let them down easy.
Make a choice.....
say, "i care for you, but i love my boyfriend more."