My exclusively breastfed 2 week old hasn't pooped in over a week. He seems very uncomfortable. Is there anything I can do? Or just wait?

DO NOT WAIT. This sounds serious and you need to take your baby immediatelt to your pediatrician or to a ed nearest you. Breastfed babies poop usually with each feed. This could be a sign of a more serious condition called hirschsprung and can lead to a toxic colon.
Variations of normal. Bf infants may stool a little smear every feed or a basinette full once every 7-10 days. As long as its soft , it can be normal. If baby is wetting diapers every 4-6 hours & feeding well, you can probably wait for the inevidable. If you want to stimulate baby to go, a little vasiline on a q-tip inserted the length of the cotton & moved around in the anus may trigger a stool.