There may be 2 things going on. One, you are building lean muscle mass from running and that weights more than fat so it will look like you are not losing weight. The other is that Glutamine is a protein. Any nutrient (carbs, protein, and fats) intake that is increased and the body does not use it, it is stored in the body as fat. Suggest you start measuring your body instead of using a weight scale. You will become trimmer, clothes fitting looser, without really losing weight due to increased lean muscle mass. Recommend lower your glutamine or other protein intake. The body only needs approximately 70-80grams total protein intake (food and supplements) when you are exercising. Hoped this helped you.
I, too, consume glutamine after workouts. It's my understanding it helps with muscle recovery. I've never heard/read anything about it inhibiting weight loss.
Of course, I have no expertise on the subject but I suspect you've just hit a plateau.