Diaper Leaks...Help!!!

MsTee
Please I need any suggestions on how to reduce diaper leaks. I'm a first time mom and my son is 1 month old who weighs 12 pounds. I currently use size 1 diaper (pampers or huggies) which I believe is the correct size I'm supposed to use but I keep having leaks at the back or the side. Not sure what I'm doing wrong...pls help