I had terrible problems with DC2, it hurt during every feed and afterwards for the first 10 weeks, I had mastitis, then thrush, then mastitis.... with hindsight, part of the problem was that I knew what I was doing
but DC2 didn't. And the last time I had fed had been a lumping great self-latching one year old. I was offering my rather large and engorged breast to a tiny newborn who had no idea about latching or positioning. If DC2 had been DC1, I might well have given up - but I knew it would be easier later on, I knew how it was supposed to work and I knew I could do it, because I had before.
I also knew to keep on going to the baby cafe/breast feeding clinic rather than HV clinic, and to keep on demanding asking for help.
I had similar problems with DC3 (latching, very sore nipples, over supply - milk came in 28 hours after birth) and even with DC4 ("milk flu" on day 2 stayed and turned into mastitis by day 6) and there were many tears even with expecting there to be problems. But I took it one feed at a time and desperately tried to play the long game, to get through the first weeks until about week 12 when I knew it would click.
Also with other children about, the feeding pattern does have to adapt. Dc1 didn't do evening cluster feeds, DC2/3/4 had to as that was the only time I was sitting down long enough. They had more "top up" on the way out of the door type feeds, and less of the "I'm just going to lie on the sofa watching telly all afternoon with my boobs out" type feeds DC1 was rather fond of 