opinions on starting baby food

My baby is about 4.5 momtbs old and still waking every 2 hours to nurse. We've been given the ok to start baby food but Do you think starting to give his baby food through out the day will help him sleep longer at night? I'm really wanting to wait till 6 months to start but these nights are starting to wear my body down. If I do start, how many times a day do I give him food?