Hoping MN hive can shed some light on this.
DD is 11 weeks old. Started having regular baths at 4 weeks. To date she really enjoyed them (as much as you can tell) - smiley, relaxed, moving arms and legs in the water. We use a baby bath seat covered with a towel so she is always secured, with me or DP pouring water gently over her with a small jug. She particularly liked having hair washed. Sometime last week she got upset in the bath. I was used to her getting upset when being taken out and having a cry after but not in the bath. Since then she's been just hysterical in the bath and although we do exactly the same things she's reacting to them why such fear and upset and distressed crying I am at loss at what to do. In this hot weather bath seemed to be the best way to cool her and make her comfortable so seeing her so upset is just baffling (and heart breaking). We usually give her an oil massage afterwards which she loved but is now as distressed by it now. 
Any thoughts/suggestions/similar experiences you managed to overcome would be welcome.