Help, question.

My son is almost 2 weeks old. I have been breastfeeding and it has gone wonderfully. Every morning I wake up pretty engorged but this morning I didn't. My boobs are softer. I pumped today and only got 2oz out of 1 boob and only 1oz out of the other. 3 days ago I was pumping 4oz out of each. my son eats about 4oz every 3-4 hours. What would cause this dramatic drop in supply. And what can I do. My son is fussy today and is eating every 2 hours instead of 3-4. He has also spit up a lot today compared to normal. Any advice would be much appreciated.