Hi Sheba

You mentioned he was teething. I'm wondering if the warm bath is making him do a wee and his wee might be a bit acidic and stinging him a bit? As you probably know, teething generates a bit of acid and some babies find this a little stingy when passing urine. I know my DS does. Does he scream any other time during the day i.e. when he might be weeing in his nappy? Try getting him to drink more water to dilute his wee a bit. Just a thought.