Is my body plotting against me?

It annoys the hell out of me. Whenever I see an attractive male or female, my penis shoots straight and it ALWAYS leaves me in an awkward position. God forbid, if an attractive person flashes on the screen while I'm watching T.V. with my family and my dick goes to attention like a brainwashed marine. There have been many uneasy discussions throughout my family regarding my rebellious libido, which miraculously decides to stop working whenever I'm about to get some. Every sexual experience I have ever had has ended with me apologizing, and my partner saying 'its ok' while trying to suppress a laugh.Please Help, what am I to do???