Your physiotherapist should be able to give you more than just stretching exercises. They are the ones who should be giving you strengthening exercises too if they feel like muscle weakness is one of the reasons you're having this trouble. You can use a foam roller daily, and it can be very helpful with ITB issues. But because this has been going on for so long and it sounds so significant, I'd recommend seeing your doctor and/or physiotherapist again so that hopefully they can address the issue again.
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford
"No matter how slow you go, you are still lapping everybody on the couch."