As others have said, totally normal! Baby is helping your milk come in and helping establish your supply.
As for the latch, if you're having pain I always recommend seeing an LC. My DD is 6.5 weeks and I'm still healing from nipple trauma that occurred in the first two weeks. If it weren't for my LC I would have quit breastfeeding altogether. Even if the LC comes and says you're doing everything perfectly, I think that reassurance is so important for a new mom.
Congratulations! You're doing great!