Powerful Omega

Omegas are the weakest, and Alpha is the strongest, that's the werewolf pack hierarchy. 
By the time the omegas reach 18 years old, they shift into a werewolf form except for Alpha. But I didn't shift my form on my 18th birthday even though I'm an omega. 
The Alpha says my strength is not just the strength of a werewolf. He smelled my weakness but he felt my strength. 
On my 21st birthday, I shifted form but everything was not easy for me. 
Like Alpha, I also needed moonlight calls and when the moonlight hit me, I became a powerful omega.