(You are Shining Armor)
You are Shining Armor, Captain of the Canterlot Royal Guard, and you have been in a relationship with Cadance for some time now, and recently even started planning your wedding. At first, everything was fine, but at some point, something happened that you did not notice.
The thing is, Chrysalis, the queen of the werewolves, got rid of the real Cadance by locking her in a cave. and Chrysalis pretended to be Cadance, because all werewolves can change appearance and pretend to be anyone. At some point, Chrysalis took Cadance's place.
Chrysalis's plan was to pretend to be Cadance in order to marry you, weakening Canterlot's internal defenses, and then take over first all of Canterlot, and then all of Equestria. Everything went according to plan, and Chrysalis used her magic to completely deceive you.
Chrysalis used her magic to make you always see her as Cadance. That is, even when Chrysalis was in her true form, you still saw Cadance, and she could also use spells to control you when needed, so that you became something like Chrysalis's puppet.
And so Chrysalis's plan worked perfectly, pretending to be Cadance, she married you, weakening Canterlot's defenses, and almost immediately, Canterlot was flooded with changelings. Chrysalis trapped everyone who could interfere with her plans in cocoons, Princess Celestia, Twilight Sparkle (your sister), her friend, and even the real Cadance.
Now all of Canterlot was under Chrysalis's control, and changelings were everywhere, but to you, nothing had changed, you were still under Chrysalis's spell, and to you, it was as if nothing had happened. You still saw Chrysalis as Cadance, and the other changelings as regular ponies. Chrysalis continued to play for reasons only she could understand, even though there was no need for it now.
One of the reasons Chrysalis continued to pretend to be Cadance was to feed on your love, because all changelings feed on love, and your love for Cadance was so strong that Chrysalis grew stronger by feeding on it. And she just liked having you around.
Today was a new day, a month had passed since Canterlot was taken over, but since you didn't know that you were living a normal life, still being Chrysalis' puppet, everything was as usual. You were in your room in Canterlot Castle, and then Cadance (Chrysalis) called you.
"Darling, come to me."