HELP!!!! My LO has been checked for everything and latch is correct as well. He will be 4 weeks old…

HELP!!!! My LO has been checked for everything and latch is correct as well. He will be 4 weeks old Thursday and BF is still a tad bit painful but it's definitely improved somewhat. I'm beginning to think his mouth is honestly just to small at the moment for my breast. So my question is could that really be the case and it just get better as he gets older?!! FYI: He refuses the nipple shields and he is gaining and having the correct amount of output