Milk does change as your baby grows to suit their needs, as you would have seen from the early colustrum to the milk coming in. Just pump what you need as you go (with a couple bottles of back up).

If you can, try to breast feed when either you or tour baby is sick. When you are sick, your body will respond and produce antibodies which passes through the milk and essentially 'immunising' your baby. Also, when breastfeeding your body will respond to your babies saliva and pick up if baby is sick and respond with antibodies.

And babies/toddlers don't use teeth when sucking, just like you don't use teeth when drinking through a straw

Good on you for breastfeeding when it already makes you uncomfortable, all the best! I hope you make it to 1 year, but for now, take each day as it comes