If you have been working out 3 times a week wioth weights + cardio days too for 2.5months and have now plateaued, you may do well to take a complete rest week. A 7-10 day complete rest is generally a very good idea and reccomened for every 8-12weeks training. Although between workouts you're body will recover, after a few months of contiinued training it will do you best to take a complete rest. That way you're body can re-juvinate and will again feel in a state of calm (rather than continually stressed thru workouts and cardio). After which get back into training; keep up the weighjts to maintain muscle mass but perhaps cut the cardio down (or out completely). Then you may find your body begins to let go of fat again.

Regards your diet; 15% carbs is very low! and may be another reason you're body is struggling to feel 'stress free' enough to let go of fat. It may have worked in the past but perhaps more carbs to boost you're energy levels and fruit & fibre intake may do you good.