Yes, the pressure in the breast as the let-down came wasn't exactly fun, and yes, there were plenty of times in between feedings that it happened, but I just used it as an opportunity to pump if my little one wasn't hungry or was sleeping, or if they were awake I'd just feed them. There was no set schedule, I gave them what they needed on demand, taking my cues from them, instead of forcing them into a schedule that suited me and my convenience (and could therefore be totally wrong for them).
Every pregnancy, baby, and nursing period is different - don't ever forget that.
Good news is that it will adjust as they develop and their needs adjust.
Being tired is also normal, as much of your nutrients and fluids are being used to synthesize milk for the baby, so don't sweat it.
And watching a 3-year-old and nearly-2-year-old shouldn't be so bad with a baby, as I'm sure you've begun to teach them responsibility and the that every action has its consequences, good or bad. I would especially think so on the part of the 3-year-old, since by now they are walking and talking and can at the very least understand simple directives and that other people have feelings too. You're not a slave, and they're not the pampered pets of the priesthood, they can only run you ragged if you let them.