An off the hip opinion from a guys point of view is that he was friends with you because he wanted to be more than friends. His blowing you off now just shows he is being true to himself, he wanted something more from you and when it didn't develop he he found someone else. Obviously he classifies you as girlfriend or nothing . . . although it may be past the point of it ever working out for you two on that level.
He didn't want to be "that guy" . . .
Where do you stand, you say you love him with all your heart, but does that mean you would want to be dating him? Because it seems so in your post. Depending on how into this girl he is and how competitive you are comfortable being, you may want to tell him where you stand.
Looking back on what I have written it seems a little harsh if you are hurting . . . but it is truthful.
I'm sorry that happened to you but you really need to be true to what you feel, if you "like" him you need to make it clear before he is too serious with the other girl, if you just want to be friends, your best bet is to be persistant without giving him attitude because he is now hurting you . . .
Although I keep thinking of a similar situation I have been in and I still really don't have time for the girl even though she called me a bunch of times . . .
Good luck