Are you playing normal or Expert mode?
On normal mode he's kind of a joke, here's how you beat him every single time:
Make yourself a little cage suspended in the air. Make sure you have a layer of solid blocks above you to block his sweeping eye laser.
Now, sit in a pool of honey, and also put a campfire and a heart lantern near yourself. You should use the Beetle Armor (with Shell for max defense), the Celestial Shell, Charm of Myths, Worm Scarf, and any of the following: Warrior Emblem, Destroyer Emblem, or you can use Paladin's Shield or Flesh Knuckles for even more defense. Reforge all your accessories to Warding if possible. If you are missing any of the items I mentioned, don't worry, you don't need every single one of them, but you should have around 90-100 defense. Note that you are sitting in a box, so you don't need any mobility items such as wings, boots, or mounts! So maximize that defense, followed by attack!
Buffs: Lifeforce Potion, Endurance Potion, Ironskin Potion, Regeneration potion, and a food item. If you don't have all of these, again, don't worry, you don't need every single one, but try to use as many of these as you have. The food item you should always have since it's so easy to get some kind of food.
Strategy: you are simply going to sit in your box and tank his hits and stab at him with the Solar Eruption. You will have so much defense and health regeneration that the nurse is completely unnecessary. The only thing you must pay attention to is that you must not kill his hand eyes too quickly, or else they will turn into the invincible True Eyes of Cthulhu which are a major pain in the
. Instead, try to kill all 3 of his eyes at around the same time to minimize the time the True Eyes of Cthulhu can damage you. Once all 3 eyes are defeated, stab at his heart furiously until he dies. With all of your buffs you will kill him faster than he kills you.
This method requires close to zero skill and can be used over and over to farm him. Enjoy!