Today I had my thrid month weigh in and i gained the pound that i lost back . Is my insurance going to deny me?

No, I don't think they will. The 3 or 6 month diet required does not affect your eligibility. They will always go by the weight you recorded at your first visit. However, they do want to see that you are committed to a healthier lifestyle and to weight loss. I would really try not to gain a lot of weight during your supervised diet.