Firstly congratulations. It sounds as if everything is going really well.
Agree with Wendy. If he's only 3 weeks (age corrected) or actually - 9 weeks for normal babies, waking every 3 hours during the night is doing well. He's not ready to go longer - his tummy is still very tiny and needs feeding during the night. 2 night feeds is normal for this age.
Try and rest when he does. Forget about the housework etc.... I'm off for a rest now and DS is 5 months and wakes around 3am and up for the day about 6.30.
alex