Why is this bothering me?

One of the guys here at work got married at the weekend.  None of us were formally invited: they are both in their 60s, it was a small, quiet celebration with their close friends.  Except one of my colleagues was invited, the one who is also my next-door neighbour.  And, apparently, the ex.  With his new girlfriend.

I'm good with that, they were friends, and neither do I have a problem that he has moved on and has a new woman in his life.  Good for him.

What's bothering me is that my neighbour simply cannot keep his mouth shut and my ex is probably now gleefully aware that I, having been the instigator of the break-up, am still single and he isn't, and b) have bought a house and am spending a lot of time there.  It's no big secret, I am very happily single and the break-up was never about anyone else.  Ditto the house, no big secret.

So why is it annoying me that the ex now knows all this?

Actually, you know what?  I think it's annoying me more that it's annoying me.