breastfeeding rant

I was planning on breast feeding for at least six months with my newborn. Isn't hubby and I were planning on having me be a stay at home mom but plans changed and I'm starting work tomorrow! I haven't pumped very much so I don't really have a stash. I want to cry at the thought of giving my baby formula. I always believed breast is best and I loved the closeness of having my baby right there. Now I have to let my mother watch him while I'm gone and he's not getting the same nutrients. I just feel like I'm failing as a mother ..