I am not an expert, but I think it is GREAT that you only gained back part of the weight! I took a break from the phen and gained about 6 lbs in less than 3 months

Of course I have been doing a boot camp for the past 6 weeks that consists of lots of weight-training so am not sure if that is all fat..that's what I am telling myself anyway!
I just started back because I really wanted to get the rest off! The phen really helps me to make better food choices and not snack as much. I think that as long as you take it KNOWING that you can't take it forever and that it is only a "learning tool" that it is safe for you. Hope this helps!