Your calorie deficit is significant. Aside from your metabolism slowing down, your body might digest muscle tissue for energy. It's possible that you are in a state of ketosis, in which your body is now burning fat to produce ketones which the cells burn to fuel life processes. People in ketosis often don't feel hungry. It's an effective way to lose fat, but you still need protein and carbs & essential fatty acids in your diet to stay healthy.
Could you ask or pay the trainer to help you determine the right mix of fats, carbs, and protein to get you to your goal? Good luck