New here. I’m a chubby girl. My boyfriend is working out and I feel like I should too. Am I right?

New here. I’m a chubby girl. My boyfriend is training for a marathon. I’m tired of feeling like a complete fake and I feel like I should try to be healthier. I’m terrified because of the way I’ve always been with food. I know I’m being the “lazy tier” chubby girl because of this. I know I’m doing it all wrong. What do I do?