I remember that my DS used to pull off and arch his back when he had wind pain - and after leaving him upright for a minute he would almost always burp. We actually worked out a way to breastfeed him in an upright position and he would burp and feed at the same time!! I think as they start to empty the breast quicker their tummies can take a while to catch up!
They can also do this in frustration, I believe, as they start to empty the breast quicker and they get annoyed when there is no more. If you know there is plenty of milk there I would say that it is wind related.
Probiotics (aka 'friendly gut bacteria') are very effective at easing digestive upsets. If you were treated with antibiotics during or after birth, antibiotic residue is passed on to bubs via the breastmilk, killing off some of their vital probiotic bacteria, as antibiotics effectively kill both good and bad bacteria - they cannot discriminate between them. To replace their (and your) friendly bacteria you must either supplement with a probiotic yourself (which will pass onto bubs via the breastmilk) or add some probiotic infant powder to his EBM. Our breastmilk naturally contains probiotics in the early stages- but exposure to antibiotics kinda screws that up! Unfortunately Obs etc will not inform you of this when at hospital.
You can purchase probiotics from health food stores. Must be kept in the fridge. Check out InLiven in the belly belly store.
HTH.

Congrats on exclusively bfeeding and working full time - I imagine that's no easy feat & takes dedication and sacrifice- very admirable.