How to restart lactation!

So I had my baby sep 2nd and she never was able to latch so I always pumped, well by time she was 1 1/2 months my supply tanked and I had to quit pumping. I have felt non stop guilt about it as I was able to breastfeed my son for 2 years... can I restart lactation by exclusively pumping? If so, how?! Please I really want to be able to do this for her..