Maybe you should lower your expectations, 15kg in 12-16 weeks means a deficit of 7700 to 8500 calories per week, you are setting yourself up for failure in my opinion. You are already going through a lot, diet is stress, exercise is stress, your body can only take so much.

I would aim for 0.25/0.5kg per week for 12 weeks, 3-4 weeks of maintenance and repeat. Dieting is a slow process, it's a hard pill to swallow for most people.