Why do I get stretchmarks so easily from working out?

Warioman Asked: Why do I get stretchmarks so easily from working out?So I'm 16 right now and I have stretch marks on my lower back, upper back, buttox, inner thighs, shoulders, delts, sides of my chest, hips, entire inner biceps, inner parts between forarm and bicep, knees, and behind my ankles, and maybe some other place I can't remember at the moment. The point is I got all of these stretch marks from lifting weights. I went into my gym hoping that I would get lean and muscular, but dofar I've only gotten this huge conglomeration of stretch marks. I lift moderate weight,

acne