Percy Jackson son of Chaos

Where did I go so wrong???

Percy POV
It all started when my stupid half-brother turned up at camp.
Flashback
I was on the lava wall, when I heard the conch horn blow twice, an attack.  I jumped from the top of the lava wall.  Using the training at camp Jupiter I turned the fall into a double front flip and turned the landing into a roll.  I turned my sword from it's pen form to it's sword form.  With my celestrial bronze sword lightly pulsing with light out infront of me, I reaches the top of half-blood hill, right next to Thalia's tree.  I saw a child about my age running towards me with an army closing in on him.  He got to me, pushed me towards them and I was put into a choice of kill or be killed.  I destroyed the whole army, barely sweating and covered in golden dust.  The boy ran towards me and tried to grab my sword from me.  The whole camp turned up and Chiron yelled,
"Perseus Jackson, what do you think you are doing, give the child his sword back!" Annabeth came running down, grabbed the sword out of my hands and gave it to the child with a kiss.  Then all the gods showed up with my father at the front.
"Percy, how could you do this, to me?" He wispered.
"Do what?" I asked.
"YOU DARE LIE TO YOUR OWN FATHER?!?" Bellowed Poseidon.  "You know what, I can't look at you and call you my son.  I, Poseidon, God of earthquakes and ocean, disown Perseus Jackson, son of Sally Jackson."  As soon as Poseidon had finished, Percy felt his power drain out of him and as soon as he felt all his power leave him, a glowing green trident appeared over the other child's head.
"I, Poseidon, God or earthquakes and the Ocean, claim Barry to be my new representative."
"All hail Barry, Son of Poseidon." Everyone chanted.
"Now Perseus, you will die." Said Poseidon, just before all the gods threw there weapons into my heart, as I fell backwards, a portal opened and swallowed me.
'At least I have the gods weapons now' was my last thought before I blacked out

This is my first book so please don't be too hard on me but don't go easy on me either.