Baby throwing up frequently?

Hi guys. Just had a quick question. My baby is breastfed and two weeks old. He started having issues with vomiting last Friday. We took him to the doctor and she said it was either a virus or he didn’t like something I ate. Well he’s continued to vomit about every other day, usually just once a day and tonight he puked up a lot of mucus with the breast milk. Any ideas on what could be wrong? I’m at such a loss. Thanks