By JAN JARVIS Diana Mays has a high-stress job and a lifestyle that leaves little time for cardio workouts.The combination led the Arlington teacher to a mobile health-screening service. "I wanted to find out how far I am away from a stroke or aneurysm," said Mays, 59. "I feel like those are secret things that go on inside our bodies."Mays is among a growing number of adults who are bypassing their doctor’s office and paying hundreds of dollars out of pocket for health screenings.