Mending not working on the Fishing Pole.

Been fishing with my pole and the durability has gradually gone down instead of up.

The Pole has Luck of the Sea III, Lure III, and Mending I.

Edit: I Found that Mending does indeed work after killing a creature and getting its exp. However, it does not feel like its working while fishing. Fishing is one of the fastest ways to get exp and it seems to do no good at all for the fishing pole.