Constipation before camp… (quickest remedies you know)?

please help! im going to camp tommmorw. and i need to get this poop out of me! i know that sounds nasty, but im really fed up. Im 14, and for the past three days ive been eating Activia, and Raison Bran for breakfast! and its not helping!!!!!!!!!
I literealy just shuved 3 prunes into my mouth right now, and im really scared. I don’t want to have problems at camp (and i normally do anyways, because the toilets are so damn nasty)
PLEEEEEEEEEEEASE HELP ME! thank you! i need fast relief in about 10 minutes,
its a sleepaway camp for 3 weeks