Why am I obese and have heart conditions at 13 when I'm not unhealthy!!!!?

Because I'm 13, 5"5 and weigh 197 pounds. I have big boobs but I shouldn't weigh that much!! I don't eat unhealthly and I excise alot. My doctor told me today I'm obese and need to lose weight. He also told me I need to go for hospital tests as my heart is in really bad condition as a result of my weight and I have just been diagnosed with type 2 diabetes. I don't get why my liver and heart are in bad condition as I exercise 3 times a week for 2 hours and eat what I should be. Help!!!!!!!!!!