Do i tell him the truth?

like a lot of people are saying you need to tell him but the best way i thing you can tell his is in an environment where you are comfortable, the best way to tell this chap is to come and and say that there is something that you need to let him know about yourself and let him know how old you really are and and how you were scared that revealing your age to him when you first met you though that he would run a mile but if he really likes you then he will understand as age is only a number