How can I avoid having to use the bathroom during a long plane trip?

-New York to Rio(Brazil)....I'm always in the window seat boxed in by sleeping parents and older sister sits in next row(shes in high school). I'm shy/embarrassed about having to make scene about going on the plane.Antes de viajar va no banheiro do aeroporto e fike 30 minutos la pra solta tudo mais talves ira 1 ou 2 vezes no banheiro :)
I bet your parents and sister get up sometime. Get up when they do. It is unhealthy to not go for that long and to not stretch your legs.
Bring a large bottle. discreetly pee in it. Then, drink it. No one will ever know!!