Tips for fixing a shallow latch?

Vegasbb

I've been having trouble getting LO to get a deep enough latch lately and it's killing my boobs. Advice please? I know what a good latch looks like, he just opens his mouth wide and ends up just closing down on my nipple - no idea how to make him do the right thing. 

ETA : I always try making a "nipple sandwich" but he refuses to latch when I do this. He just shakes his head and gets fussy until I get my hands off the nipple.