How do I lose weight in my stomach and waist area?

I am 5’5″, 161 pounds and I have a huge stomach. I would love to lose about 70 pounds so I can weigh closer to 90 pounds and have a flatter stomach, but I’m worried about having gross saggy skin. I have already lost 15 pounds.

I want to lose weight and tone up my stomach. I’ve tried crunches, sit-ups,and everything but nothing works.

Help!