Let's turn this around: Let's assume this was his depression (and not the fact that he's simply not interested anymore), why do you want a guy who's so mentally unstable that he'd push you away? At the very least, you should expect a partner to be keeping his depression managed and not push you away when he feels like it.
But if you do want a guy who'd do this to you, I suggest you don't contact him. He already knows you're there and that you're open to having him back. Leave the ball in his court. If he does come back, you want to know it's because HE wanted it and not because you asked for it. Besides, having a bit of dignity and not reminding him that you're still available is a better look. And there's something to be said for being distant and allowing him time to miss you.
Lastly,if he does come back to you, do not accept him unless he's done some major re-thinking on his life and the way he's managed it. You want to be confident that this won't be a yearly occurrence
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.