It sounds like you have a connection leak.
You should monitor the pool statistic and see whether the number of used connections will grow ovber the time.
Also you might have a look into these:
https://community.jboss.org/wiki/CanJBossTellMeWhenIDontCloseAConnection
https://community.jboss.org/wiki/WhatDoesTheMessageDoYourOwnHousekeepingMean