Pimples accure either from stress, from not washing your face/body thoroughly enough, through genes ( naturally oily/sensitive skin), or hormonal change (which can not only come from puperty but also stress etc). Pimples can even form from your diet. Like chocolate is said to cause out breaks/make them worse, as well as being over hydrated. Even though you are 20, you are still growing. Men are not fully grown until about 23 (if i remember correctly). You could be under more stress then usual or you may not be washing your face good enough, thus clogging your pores and creating pimples. There are many reasons on why you are breaking out more. Also you CAN pop them, you just can't pop one that isn't 'ready' if its a white head it doesnt take much force to pop- thuse it will not scare. Being a girl- I pop mine I get them and then wash my face. So far I have not had scarring because of it. But anyways- if it really bothers you go to the derma. they can give you meds/ ideas on what to do to make your break outs not as bad/ go away.