I plateaued at 68kg for AGES, and I thought it was just the weight I was supposed to be. Then after putting on 6kg I decided to pull my finger out and lose what I'd put on, and I kept going and now I'm at 66kg... so I think you might just need to shake up your routine a bit! That's what I did! I changed my eating a bit, started counting kJ instead of points, different foods and actually paying attention to how much Fat/Protein/Carbs/Fibre I was eating.
Maybe shake up your routine a bit??? Try a new exercise, introduce new (healthy!) foods to your diet, get out of the plateau. You can do it