Why do I stink? Please help me out?

ok so this bad smell just comes out of no where like about 3 weeks ago. I smell it and others around me smell and it's so embaressing. But the thing is I only smell when I'm at school in my classes in the trailers. When I go to any other class inside the building I don't smell. And I don't smell on the bus. Thank god I only have 2 classes in the trailers. But why is this. I never had this problem before. I shower about 2 times a day with soap. I use deoderant and perfume. Please help me. This smell just suddenly appeared like I said and it's so annoying.