OP I had a tummy infection years ago where I'd be okay for a couple of days then I'd end up with the runs again, then okay, then not, ITMS. I needed to go on ABs to get rid of it, as in the end I dropped 8 kgs over three weeks.

It had similar indications to other infections, I ended up with almost green diarrhoea in the end. But just the fact that I couldn't seem to get rid of it was enough. It was quite bad at a couple of points though.