It could just be transient stomach bug followed by temporary lactose intolerance. My other half, N&D, has to avoid dairy products for a week or so after a stomach bug and then gradually reintroduce them. The doctor's explanation is that the villii which help in lactose digestion atrophy when you get a stomach bug, and need a chance to recover. N&D finds things like yoghurt and hard cheeses easiest to handle, with milk hardest. So maybe all you need is a short break!