He's not seeing anyone else
It's been awhile now so what's the problem
Maybe he is just afraid that things will change for the worse or perhaps he thinks that you won't give him a positive response?
You could be in the friendzone.
You shouldn't think about this any longer than you need to. :) He'll ask you out when the timing is right. Hesitation is generally because he's nervous and wants to make sure you're 100% in it as well as himself. If it's worth it, it'll take time. He wants things to go perfect because he does value your "relationship".
Be happy that you're with him regardless, and let nature take its course.
Just ask him.
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