Sudden self-weaning?

My LO was happily nursing in the morning and before bed and for two days now just started refusing the breast. The way he makes a face at it made me think perhaps something changed with my milk but I'm definitely not pregnant and he will take my milk expressed from a cup or bottle. I've kept offering but no pressure. He turns his head to the side and makes a face like no thanks. I've heard that child-led weaning happens slowly rather than all at once so I'm a bit surprised. Happy to follow his lead, but wanting to rule out teething. Has anyone else had this happen?