I am a sixteen year old male. I weigh 278.5lbs and am 6'4.5". I have stretch marks in every place I can think of besides my face (so far). They are showing up on my hands, groined, knees, fingers, under arms, biceps, triceps, back going vertical and horizontal, sides, thighs, legs, and are very painful when they come... which is how I know Im starting to develop one that is very small on the right side of my neck. I don't know what to do about it, I diet (don't lose weight) exercise (don't lose weight) but at the same time, Im really not very big at all, giving I body build but have gained fat and fat weight. Does anyone have any ideas as to what might be causing this?