At what age is the most common/main/knowin for people to suffer from depression?

Like just to feel REALLY BADLY down about their WHOLE life & go through a real bad time, even having suicidal thoughts, for me, it all started coming on around about 18, (after i had a child) im now 21 & still depressed over my body, my life, money, bills, in debt, family, friends, threats, anxiety, fear, & lots lots more. what age would you say its common for people to get depression? when did it start for you if you ever got it? & how did you get better?