Can someone tell me how to beat nasus?

Everytime I fight nasus I play someone who can poke him down or chunk him repeatedly but with innate lifesteal, flask, and health pots he heals like he's gone to base. It seems like it's unwinnable. Also if you poke them with autos the minions agro you and do a ton of damage. Eventually because he is zoned the lane eventually pushes to his tower even when you arent pushing, making it safe for him to farm again. Can someone please tell me how to beat a nasus in lane, not just tell me champs that work because i feel like everytime i see him it's a loss.