I like my bestriends Boyfriend, What should i do ?!?!!?!?

ME and this guy went out last year for a little. Then a little whil ago he started going out wih my friend, now i like him again. Do you think i should tell him, or wait. He always talks about her to me, today he told me he loved her. It hurt me. i want her to be happy, but i like this guy ALOT. What should i do?