Breastfeeding help

My baby is 3.5 months old and started sleeping longer stretches. He’s exclusively nursing and I am not pumping, so him sleeping through the night is sooo painful! It’s been a while now and I wake up in the middle of the night soaking wet and my boobs are rock hard. So hard that it’s hard for me to even hand express. Will my boobs adapt to this so I can start sleeping too? I hate to be waking up even though my baby is sleeping! Last night he went to bed at 7:30pm and at 5am I had to wake him up because I was in so much pain, but he would for sure have slept longer. My other question is… will this drastically affect my milk supply or still ok because he’s likely eating more during the day?