Runner's Training Tips: Hamstring/ glute pain!

Hi all, I'm hoping that someone may be able to give me some advice...  I ran my first full marathon in june, and my training had gone amazingly well!  However, about mile 8, what felt like my hamstrings tightened up on me, and I was in extreme pain through the finish.  The pain is right where your glutes meet the hamstrings, so i'm not sure if it really is a hamstring muscle, or a glute muscle.  It seems to be a very hard part to stretch also.  I am still having pain, and it has been just over 3 months since the race.  Any suggestions on what exactly it may be, or any help on getting it to feel better?  I've done massage, ice, and stretching, but i'm thinking there may be a different stretch or combo of things...  thanks for any help!  I'm running a half on Oct 5, and the CIM on Dec 7, so i'm hoping to feel better ASAP! 

Mary