Marriage Struggles...

So I've been married for twenty years now... To be honest, we haven't really had a 'sexy' relationship in the last decade. It's not that my wife doesn't desire me anymore; it’s just that our lives have taken different paths and we’ve kind of drifted apart romantically... We still sleep in the same bed every night though... Last month, I met someone online, someone younger, more adventurous... And she understood my need for something new... something exciting. She said she wanted to explore my fantasies with me... It wasn't real-life or anything serious, it was just a way to reconnect with myself and indulge in desires that have been buried under the routines of life... But one night, we met up... I'll be honest, I did some things with her that I never would’ve done with anyone else, things my wife could never even imagine... It was thrilling, but also scary... because afterwards, all these feelings came flooding back, guilt, confusion, and a fear of what comes next... So now here I am... torn between my long-term commitment to my wife and these new desires that have come alive in me again. I love her so much, but at the same time, I can’t ignore who I am... I feel like such an asshole for even thinking this way, let alone acting on it. So I’m asking you all, am I really just a heartless bastard here? Or is there something more to consider when you’ve been married forever and suddenly find yourself wanting more than what’s been enough for so long...?