My baby is 5 mth now and I want to join back for work. Am I being selfish , should I wait till he is 1 or 2 yrs?

no i do not think you are selfish at all. you are a mother, but you are also an individual. the fact that you want to get back to work means that you want to get independent and take charge of your life. the one thing that you will have to look after is the type of care arrangement you want to make. if there is someone at home or if you want to place your baby in daycare, you will have to take care of all the arrangements before you get to work. if you are not sure yet, you can wait till the time your baby is comfortable with weaning and eating other foods other than breastmilk. and remember, when your baby realizes how hard mamma is working, both at home and at her other work, he or she will look at you with renewed respect :)