Well for starters, exercise will not only help your weight but it'll also help your heart, mind, and soul. Make the time for it, even if it's as simple as walking for twenty minutes per day.
Not many people can be entirely devoid of junk food so congratulations to you for conquering that obstacle. Weight is just a number but if professional doctor's are dubbing you obese then you may very well have an issue. Obesity is dangerous, it means you're in that ever growing category much of the population is now delving into. Of course it's hereditary, are your parents and siblings overweight also?
You're aware of this but all you can simply do is drink water, exercise moderately, eat the essential fruits and veggies, and keep a stable mentality. If worse comes to worse you can try a diet pill or hire a professional trainer. Best of luck.