Re: Sudden crying when nursing!
You say walking him around calms him down, have you tried nursing in motion? Nursing while bouncing on a ball, swinging back and forth, walking, etc. That gets tiring pretty fast, but some moms have good luck with nursing in a sling or wrap or Ergo carrier. I couldn't really get the hang of nursing in a carrier so I would just walk and nurse around until he calmed enough so I could try to sit down.
Alternately, it may be painful to nurse in certain positions. Maybe keep playing with positioning if he seems uncomfortable in a particular one. Teething could very well be beginning, teeth move around in the gums long before they break through. An ear infection could be the culprit as well, especially if one position is worse than others.
mama to a little raccoon, born under the full moon, Nov '11