Newborn bowel changes!

Hailey • Mother of 3 amazing children! 👦 03/04/10 👧 04/29/12 👶 01/07/16 ❤️️
My son is 2 weeks old, we are exclusively breastfeeding and for the first week everything was perfect, no discomfort, no gas and lots of seedy yellow poops! But now for almost a week he seems to be in discomfort very often and when he poops it's slightly more green and liquidy.
Never had issues with my 2 other children so I'm kind of at a loss.
Any insight??