My DS, 2.9, is sitting on the potty willingly, and often doesn't want to get off. Sits there for quite some time if we sing songs or look at books or have some toys. However there haven't been any wees! Even if I put him on almost straight after lunch and he sits for 30 mins, there's still no wee. He somehow seems to be able to hold it in as I can't believe he has never needed to go in all the times he's sat on the potty over the last few weeks. Not sure how to encourage him to go. Have tried running the tap and giving him a drink. Any ideas?