Baby is 4 days old. When could I start to pump?!

As of today my breast of been hard and lumpy and really sore so I'm thinking my milk has came in. I do want to breast-feed but I also want to pump so if it at night I'm too tired I have an option to give him a bottle. For me it's more about him getting breast milk I've already felt bonded with him. Anyways, when could I start pumping? I think it's to soon right now. Mainly because that's what a breastfeeding consultant told me and the Internet. Lol anyways advice?