Is there such a thing to get my nipples ready for breastfeeding before I give birth and when can I start, what can I do ?

This is my 3rd pregnancy and I've tried with both of my previous babies to breastfeed but I always have problems breastfeeding with short nipples, baby doesn't latch etc. Mastitis, painful nipples. Latching can take up to half an hr. With my first I got to breastfeed for 3 weeks with my 2nd I got to breastfeed for 6 weeks.

I just want to be able to breastfeed easily. Is there ways I can start from now I'm 25 weeks..