He was an alpha and you were an omega, it was actually in your nature to choose an alpha and let him breed you, but you didn't want to face that fate...
You took medication to suppress your heat and also your typical one Omega smell... Everything was working great until the day your medication stopped working and John Price, the strongest alpha in the base, stood behind you... Attracted by your smell...
"You're an Omega... Why didn't you tell me...?"