Is it weird that it still pisses me off to see a picture of my ex's new girlfriend on facebook?

I mean, it makes no difference to my life whatsoever what, or who, he's doing.
And I'm the happiest and most stable I've ever been in a relationship right now. I've killed the 2-month curse and frankly, he's amazing with how tolerant he is of my increasingly-frequent displays of raw emotion, be it good, bad or somewhere inbetween, and I love him for that....... But there's still that little voice that whispers in my ear, saying 'you weren't good enough for the last one, and she's the better version of you'.
I still tell it to nick off, but it pokes its way through my self worth and niggles at me every now and again.