You obviously are a thin guy with a stomach problem but I wager that is more due to 1) body shape (endomorphic* v. mezzomorphic) and maybe years of overindulging. The only exercise that targets the midrife is sit ups - 100s and 100s of sit ups. Maybe some pilates to strength your core. Overall you look very thin and fit.

*endomorphic body shape tends to carrry fat around the stomach and hips. If this makes you feel any better, its actually a good healthy shape, more so for women, but men too. Suggest you start doing shoulder lifts to broaden your shoulders and lat pulls to widen your back so your waist appears smaller (if you can't change it hide it!). But all in all, you look fine.