My heart goes out to you, honey. I know that is a risk with LDRs, but the reality is, I think you will begin to see your relationship for what it truly was as time progresses.
Here is the bottom line: you need to ask yourself one question – would you have started a new relationship while you were with him? If your answer is No, which I presume it is, then you and he didn’t really have a well-balanced, equally reciprocated relationship to begin with.
That is important.
It doesn’t matter if you are the sub and he is the Dom – your appreciation for, and commitment to, each other should be reciprocated and equal. Obviously, he was in the headspace to look elsewhere, which tells me he was not the guy for you, or if he is the guy for you, he is not the guy for you, right now.
This doesn’t mean he is a bad guy. It just means you were more committed than he was. In time, it would have crashed and burned for that reason alone. If he comes back to you, it will be under a better foundation and you should demand an equal share of give and take. If he doesn’t, oh well. Somebody else will give you that reciprocation.
Good luck – you deserve the same respect that you give, no matter what.