Has anyone Reestablished Milk supply by pumping only?

I am 15 days postpartum. Baby girl has been bottle-fed since birth but now I am feeling I didn’t give breast-feeding a chance and I want to try to give her breastmilk Being as she is constantly rooting at my arms and chest. She is also always gassy. I am feeling guilty about not breast-feeding her from the start and now Regretting Not taking advantage of my own milk. I have only gotten her to properly latch once but I have flat nipples and I don’t believe she got any milk. I have ordered a spectra S2 pump and I am hoping to reestablish my milk supply that way. If she continues not to latch will the pump be enough to get my milk back? Looking to hear from someone who has been in a similar situation and was able to do so. Thank you!