Hello, after 3 months the lactation stabilizes and the milk it is produced instantly and you don't have the breasts will no longer feel full but don't stop breastfeeding! The milk is produced on the demand and offer principle. Also the baby will saturate faster because it will suck more, if until now he used to eat almost half an hour he can eat in 10 minutes now. You have to check if he has daily poo and 6 pee per dayz if he is growing in weight and after he eats if he seems full or hungry. If he is full, growing and the diaper ok you don't have to worry, you have enough milk and there is nothing to do, you will get used with your breasts feeling like this. Hope that this helps!
I am not a doctor I am only a mom who was in your situation, now he is 7 months old and he is still breastfeed.