Help?!!

So I'm fifteen and I'm on the pill without my parents knowing. Before school let out, I got three packs from my teen Heath center. They link with the public Heath center that's downtown. My nurse told me to call once I'm on the last two weeks of my last pack so I can go in and get a refill. I'm starting my last month today and I dont think I can get the pills. I'm not allowed to ride the city bus as many people get kidnapped and raped on the bus. And telling my parents isn't an option so please don't suggest it. I am going on a trip around the last two weeks of this month so I'm thinking i should make an appointment soon. Do you think I should go off the pill until school starts mid August? What do you think would be the best option besides telling my parents?