I just wanna lose my stomach

No matter where I go someone is always asking me how far along am I and when am I due. I’m so over it. I’ve been between 90-105 pounds my whole life even when I was pregnant with my first child I never gained weight. I started gaining weight after I had my daughter whom will be five this year. I like my weight and see nothing wrong with it but I’m so sick of everyone asking am I pregnant 🤦🏾‍♀️🤦🏾‍♀️🤦🏾‍♀️ what do I need to do to tone my stomach up???