I'm surprised it lasted this long. Still, just cause she says she is a virgin, doesn't mean they are gettin down and dirty constantly. Heck, I know a number of girls that say they are virgins but everything else under the sun. I highly doubt that he would have stuck with her this long without getting some nookie in some form or another.
As for the ring, 100k is nothing to a guy who makes millions a year. Britney probably spent that much on makeup last year.