I need to un-stretch my skinny jeans!! (oh i'm a guy btw lol)?

Okay so about a month ago i bought this $40 pair of grey levi skinnies from JC Penny. Now they look more like Straight legs. idk why but this happens whenever i get skinny jeans. i know i am definitely not fat but i 'm not skinny either i'm an average 14 year old boy (i weigh like 145 and i'm 5 foot 9) my jeans are really stretched around the ankle area and around the knee area. i tried washing and hang drying. i tried sewing them, i tried washing them in really hot water (but the label says wash cold so maybe i made it worse?) since this continuously happens maybe i should just stop buying them? but if anybody has any ideas (one i haven't tried plz lls) i'd be very happy!