Katie's behavior

In the last couple of weeks, Katie has been having these breakdown episodes where she just starts crying or screaming. She won't tell us if anything hurts or what happened though. All she will say is she does not want to talk about it and if you ask her about it she gets very upset again. The other day we were swimming in the pool and I was holding Katie and she just started screaming and crying. She wanted me to give her to mommy and she would not let me look at her or talk to her. She acted like I had done something to hurt her but nothing had happened. She kept telling me to go to the deep end of the pool, which is very weird for Katie, because most of the time she only wants me to hold her in the pool.