Please explain?

I;m having problems with my underwear, basically i need more support and less "movement".
Recently i had an embarrassing moment standing at the traffic lights waiting to cross a busy highway when my penis decided to get active. I had boxers on underneath a pair of relaxed pair of pants which meant well, there was no control and i had to run and sit down somewhere to let it pass.
Male version of a period cramp.
Boxers are great to wear round the house in summer.
I have a ton of underwear, mainly those tiny low-rise things and bikini-cut from the good-whore-days, but now with er, age i'm finding i need comfort more than seduction besides they can't seem to hold everything in anymore, it just spills out or pubic hair gets stuck in the elastic, eeeck!!.
This pair looked weird although i'm tempted to get this with it's 'butt-enhancing' pad but i don't want any embarrassing encounters.
Basically i've spent all night searching for a good pair of underpants that hold everything in place and keep it there.