He's doing exactly what a good man would do: He's making sure, through his words and actions, that he refuses to be your puppet.
Note the phrases you used in your post:
- This was my choice, as I felt I was not ready for a relationship;
- I finally decided I wanted to get serious.
Nowhere in your post is it mentioned that he's had any say in the matter.
You've essentially put him on hold, even after he had made it very clear that he wanted to be with you.
Now, it seems you've changed your mind.
He's probably making the assumption that you're playing games with him. I personally don't think you are, but I can easily see how he may think that.
So he's backing off, taking back his power in the relationship.
This is good,
very good, for your relationship, because it shows that he's got a pair and won't be jerked around by your indecision.
If you get him back - and it's, at best, a 50/50 chance right now, given how you've treated him in the past - hang on to him, because he sounds like a good man.