Do I love him? what shall I do?

Talk to both of them, separately.
Ask him how he feels, and thinks about you, then process what he says before you respond/react. Reaction comes from need and is never healthy. Respond comes from consideration for all of you, mind, heart, spirit and body, and is always healthy. Reactions lead to pain for someone, responses lead to intimacy and freedom.
Ask her how she feels about him and what she thinks about him and if he were to date someone else. Don't hide anything, but present the situation with tact. Sometimes the same information, presented differently, can result in hatred, or admiration. Take your time and seek the path that will build on your friendship, not tear it apart.

oh.you really ARE in a bad situation.
My opinion is that you first need to sort out your priorities. On the one hand there's your STILL IN LOVE WITH HIM best friend,and on the other THERE'S HE.think of what you need more in your life and is he really worth it? After all -outta 8billion people in the world,a true FRIEND is more difficult to find than a monumental crush. right?
:)