5 months and bites while Breastfeeding

DS is 5 months old and breastfed. He has just started teething.. and does not yet have any teeth, but I think will have some soon.

My problem is, that every time he feeds, he bites my nipple... and gummy bites are sore too.
I know he is only biting it when no milk comes out as a sign of frustration.. (before let down, and after the flow stops and he has to really work for the milk)

I really enjoy feeding, but at the moment my nipples are sore and they hurt at every new feed, and then get bitten again so hurt even more.

I want to know how I can teach him not to, or tell him off for doing it.   I have tried saying "No" and then taking my breast out of his mouth, but obviously it doesnt work as he just smiles and thinks that Im playing with him....

Can anyone help? TIA

Ouch!! I take them off and put them down for half a minute so it doesn't seem like much of a game. I avoid eye contact at that point coz I think that makes it seem more like a game too? Then I pick them back up and try again. Two bites in a row = not hungry, or that's what I teach them!! If she bites a second time, I move her and we read a story or something like that instead of a feed.

I had this problem with DS when he had an ear infection...nothing worked til it got better lol! No matter how strict I was, he just always thought it was a game.
Good luck and I hope you can get it sorted before the teeth come because DS had 4 teeth when he was doing it and it blimmin hurt!!!!!