Since you have had the pain ongoing for awhile now, go see a sports medicine doc and have it checked out.
Also, post a vid up of your squatting. Not sure if the trainer who checked your form is good or not.
My Favorite Part Of Lifting Is Having The Opportunity
Meet PR's: (May 2014) Raw Natural
Squat 475 lbs
Bench: 286 lbs
Deadlift: 501 lbs
Total: 1262 lbs
Squat: 495 lbs
Bench: 300 lbs
Deadlift: 520 lbs/500X5
Total: 1315 Lbs