...a slip-up? ...

I married my high school sweetheart and we've been together ever since. Never really thought about anyone else until last month when I met this new coworker... She’s in her early thirties, stunningly beautiful, and she's got a great sense of humor. We started chatting at the office more often and one day, it just kinda happened, we ended up kissing... It felt so wrong but also really right. Since then, we've been seeing each other secretly... I don't know what to do about this.. but for now, I'm keeping it from my wife....