I'm not familiar with weight training & need your HELP! My fiance lifts weights occasionally & recently had thin, red streaks on his upper back near his shoulders. He claims the marks were stretch marks from weight lifting. The marks appeared while I was out of town & looked like scratches on his back, although they weren't raised above the skin! I'm somewhat suspicious & don't know whether the marks were a result of weight lifting or perhaps infidelity! Also, can stretch marks disappear? Please help me determine whether my man has cheated on me or if I'm paranoid!