I'm going through the same just now, will be 4 weeks tomorrow. Were together 3 years.
Still my best friend, still love her deeply, but it's not going to work. The pain is easing, but very, very slowly.
I have found talking helps (to other friends, spoke to her a few times and we just end up crying to each other, and for some reason I find girls easier to talk to than blokes) Just tell everyone everything, the more times you tell the easier it gets.
Also, keep busy, and try not to be alone, spend as much time as you can with fiends.