I(18F) confused about mixed signals from a guy(19M) I’ve been talking to

Hi everyone, I need some outside perspective because I feel a bit confused.

There’s this guy I’ve been talking to for about 6 months (not officially dating) at the beginning everything felt normal and friendly but lately his behavior has been confusing me.

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We talk daily but sometimes he feels very cold and distant like I’m the only one keeping the conversation going even though he still listens and replies, other times he’s really nice, engaged and the conversation flows easily and also most of the times he says some sweet things like, "you are amazing, you mean the world to me, you are the highlight of my day"

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He also makes jokes that I can’t tell if they’re just jokes or if they actually mean something deeper for example I was telling him about a guy who was flirting with me and he said something like “if I ever end up like this…” followed by a joke that only we would understand.

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I’m not sure if I’m overthinking if this is just his personality or if he’s actually being inconsistent or not that interested and for context I tend to overthink a lot so I’m trying to figure out if this is actually mixed signals or just me reading too much into it

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TL;DR: I’ve been talking to a guy for 6 months. He’s sometimes very engaged and sometimes distant and I’m confused if he’s interested or just inconsistent. So how should I interpret this?