Ok, wasn't expecting that!
Your actions could be down to any number of things, only you know why. It could be as a result of a mental health problem, perhaps you weren't you at the time? Maybe you were behaving out of character? Were you drinking? Using drugs?
Not saying you're loopy so please don't take this the wrong way, but when I lost the plot I started drinking heavily and behaving very out of character, even at times when I wasn't drinking though, times when my mental health took a real bad turn, I cheated in a previous relationship. There were a number of things having an effect, none of which I think excuse my behaviour. But altered the way I felt at the time. I decided a break would be best, which led to permanently splitting up because being apart confirmed to me that I was happier without him. He'd done nothing wrong, I'd just grown apart from him and I needed to sort myself out, it wouldn't have been fair to drag him through any more.
So maybe you just don't love this person? Or maybe you have issues you need to work on?