You have my sympathy! I nursed my toddler through my whole pregnancy, until the end when my milk changed to colostrum and he weaned himself.

It did hurt a lot in the beginning, plus I had major nausea all the time and it felt so draining to have him nursing all the time. But he was only 10 months so we stuck it out and the good news is, it does get easier.

It didn't hurt much after the first trimester.
Just encourage him to open his mouth wide to make latch on hurt less, and maybe try nursing him in different positions, if he'll let you, so that the pressure isn't always on the same part of the breast.
Good luck!
