Diet advice?

I used to be heavier in high school, about 200 pounds. I'm 5'8. I tried the south beach for a year and stuck with it. I actually lost a lot of weight and went down to about 135. I felt that this was my ideal weight because I felt very comfortable in my skin. When I went off of the south beach diet slowly introducing carbs back I gained some weight. I went to about 145 and platued. I was still happy with my weight but I wished I had stayed at 135. Now my senior year in college and through the semesters I have been gaining weight because of stress. I still eat as healthy as when I was on the south beach but I now seem to be gaining weight on that!!. I started peaking past 150 and I freaked out. I fasted for a week and went back down to 140. Went off fasting and I’m starting to gain again. The worst part is that I already eat healthy and low cal. I really don't know what else to do, to get back to 135 and stabilize. Any help or advice? (I already exercise)