I hope I'm not being needlessly twatty as someone put it BUT it's very unfair to try and coerce someone into saying what you want to hear. Or to punish them for not doing so.
You might not see it that way but while you were ready to say what you said, you shouldn't have said it with the expectation of it being said back - because he might not be there yet.
I've been on the receiving end of someone saying I love you very early on and I honestly didn't know what to say because I didn't feel that way yet so I garbled something like you're my favourite person to spend time with I feel really lucky I met you, and they looked like a wounded puppy and punished me for it by sulking. It's not fair to say things to tease out the other persons feelings.
If you can't tell how they feel to the extent it's upsetting you then that's a problem in itself, as the relationship isn't secure or healthy enough to feel you are on the same page.
But it's very immature to press the other person to express their feelings and then think anything other than a reflection of your own feelings means they aren't invested.
So, you are an agent in your own life. You don't need to wait for another adult to tell you what to do. Are you happy to keep seeing him? Genuinely happy, without being a bit resentful he hasn't said the words you want to hear?
If you feel you've invested a lot more in him than he has in you, and you aren't happy with that then you're free to stop seeing him.