Re: 5 1/2 week DS abnormally fussy this evening...
You can keep up with a big growing boy, but you'll make it WAY harder on yourself if you keep giving bottles! If this is his growth spurt, then what he needs is to nurse all night long to increase your supply. Making up the 3 oz by pumping later just keeps you stable - and teaches him that crying will get him much easier milk. and of course pumping is harder milk for you! Maybe not this one bottle, but babies can form habits amazingly quickly. Settle down on the couch, co-sleep if possible, and nurse nurse nurse.
And always remember that babies have to swallow what comes out of a bottle, so just because he sucked down a 3 oz bottle doesn't necessarily mean he wanted all that 3 oz.
Lots of babies go through the evening fussies around this age, too - also totally normal (if not fun).
Good luck, hang in there, keep nursing!
Nursing, pumping, cloth-diapering, babywearing, working professor mama with the awesomest SAHD ever.