having trouble getting wet

i have trouble getting wet, no matter how horny i am. even when im really really horny i still dont get wet either before having sex or even when im masturbating. its really embarrassing when me and my bf are trying to have sex but im still dry after 20 mins of foreplay. im 17 and on the birth control patch and because im still pretty young i feel too embarrassed to use lube, does anyone have any tips that can help?