My Secret Nighttime Pleasure...

I've been married for three years now, but there's this secret I've kept from my wife since before we even got together. Every night when she falls asleep, I slip into our spare bedroom and indulge in a fantasy that always makes me feel guilty afterward. It involves role-playing as someone else entirely... sometimes an ex-girlfriend, other times some random woman from the internet. The fantasies are vivid, down to the tiniest details like her scent, her laugh, even how she touches herself.... Tonight was different though. I didn't just imagine her; I recorded myself, naked and alone in our bedroom, pretending to be this other person as I touched myself with a dildo that's not really mine at all... The sound of my breaths, the way my hands moved over what isn't real but feels so true, it's like I've become someone else entirely. Afterwards, I delete everything, hide it deep in folders she'll never find.... Is this normal? Am I cheating in a way that still keeps us together? I feel torn and confused...