My dad says I’m stretching myself too thin and I worry that he’s right.

I F(17) am currently a senior in high school and so far things have been great. I recently got into my school’s Beta Club(an honor society), got a boyfriend, have experienced a little more freedom due to having a license and overall socially, things have been great. My issue is with my school and extracurricular life. School recently has been hard, I’m in all honors classes and I currently have mostly Cs,work a job but I have been royally fucking up, help coach girl’s basketball but I don’t feel the urge to do that either. I ended up loosing 20 pounds with in 2 weeks and I’m worried it’s going to start again. My dad told me I’m stretching myself too thin and thinks I shouldn’t have a bf anymore. I said that it’s not him that’s stressing me out it’s other things and he told me that ever since I started dating my bf I’ve been fucking up. Idk what to do, all ik is that I’m tired, scared, and stressed.