Trying to lose 15lbs. Cardio 30 min/day; weights 20 min/day. Healthy diet. If I don't eat adequate carbs/protein/fat/fiber can't sleep at night. Why?

Easy. Exercise you do already. Switch your diet to veg, salad, fruit and fish at least twice weekly. No pasta, rice, potatoes, bread. And your switch will work. I have seen docs lose more than 100 pounds with the switch. Melatonin often helps for sleep.