2 week old having trouble passing gas and small bowel movements

I am breastfeeding my newborn and it's been going well. He has had regular bowel movements that were seedy and yellow in color and a nice amount until yesterday. The have now turned into very small bowel movements like a quarter size and it seems that my son struggles to get them out. They are still yellow in color. He has also been gassy and fussy when trying to pass gas. Does anyone know what this means? Is there something wrong with my milk? Is he not getting enough food to eat? Please help!