How can I build my resume if I wanna get into a seven year program?

Like @hatahets said, it would be nice to get a bit more information about you so we can try to direct you to some relevant programs/ECs. Right now I'm going to assume you're talking about a BS/MD program or something similar. I know you say you feel like you have no ECs compared to others but I'm sure that's not true. I'm going to also assume you have a few activities you can put on your application such as participation in clubs. If you truly have no ECs I would start with things offered at your school as those will be easier to get into and stay involved with. I'm taking about things like the Science Olympiad, HOSA, etc.

Other options would be an internship/shadowing opportunity, volunteer work, and research opportunities. Although I do realize that can be difficult given everything going on right now. Possibly look into a potential job, especially if you can find one related to what you're interested in. Check out this article that I think will be helpful for you: https://blog.collegevine.com/extracurriculars-for-the-prospective-bsmd-student/. There's also related blog posts near the bottom I think you'd want to read too. Of course, if you're not talking about a BS/MD program let me know and I'll try to find more relevant info!