Most Helpful Girl
I don't know. Honestly, I'm in a similar situation. Except my ex is extremely immature and treats me like I did something wrong to him even though he broke up with me. It's been 6 months since our break up and as far as I know, he doesn't miss me. He's never contacted me. He refused to give me closure and treats me horribly.
I think him wishing you a happy birthday at least tells you that you're on his mind and that just maybe, he values you enough to remember it was your birthday. Don't make the mistake of contacting him like I did. If he cares enough, he will text again.