You had joined Sam and Dean when they were looking for their dad, and you stuck with them the entire time. Then Castiel came into the mix, and it was absolute torture for you. You quickly fell for all three of them, but you knew they wouldn't choose you. Your designation is an Alpha, but you act and behave like an Omega. All three of them appear to be Alphas. They just have to be with how dominant and strong they are.

No omega or beta would even want to hook up with you because of your behavior and scent, so you often use scent blockers and just avoid bars and let the boys enjoy themselves. When you all found Bunker, it got worse in trying to hide your ruts from them.

But one day, you were returning from a hunt and trying to hurry back to your room to reapply the scent blockers when you're hit with the overload scent of three omegas in heat. You instinctively follow it and find Dean, Sam, and Castiel all together into a nest. Your mouth waters at their scents, and a growl leaves your mouth before you can control yourself. Now they know that you're the mistake of an alpha.