I don't want to lose weight anymore... what's next?

Hey everyone!

So I'm a ~59 kg, 167 cm female, I'm finishing FB Burn R2 in 2 days, and I don't know what to do next. I feel like I reached my goal weight (I started at 76,5 kg 2,5 years ago), however I still feel like I have too much fat on my body. I want to build muscles but I know that I have to eat more for that, but I'm afraid of fat gain... How do I gain only muscles and not fat, and how should I lose the rest of the fat without losing weight? I really don't know what should I do. Which FB program would suit me the best in your opinion?

I also have some problems with my period. Sorry if this is TMI, but I feel like I have to share this. My periods are very irregular for a few months now (like 7-8..), they are usually 1 or 2 weeks late, and I'm worried about this. I read a lot of this issue, and they either say my body fat% is too low (which is certainly not), or I'm overtraining (FB workouts and programs seem very well balanced so I don't think this would be an issue as well), or I'm not eating enough (well maybe...? but I didn't lose much weight for more than 1,5 years now), or another medical condition, but I really don't know which one is my problem. I want to find a workout routine which don't cause too much stress on my body, since I want to recover from this state.

Sorry if this is too long, I'm just very unsure about my goals at this point. I need someone to tell me what's best for me... :( ♥