when do you accept a guy isn't interested anymore

I feel so sad lol.

There's this guy, and he always seemed so interested in me, in person. He always tries to get me to stay a little later, really seems to enjoy our time together.

But he never initiates anything. He barely responds to my texts.

But also, I don't know him that much, he's never had a boyfriend(he's 21), and we both have exams.

So I can't tell if I'm just attention needy and impatient, or I'm getting signs he's no longer interested.

And I have asked, and he did say he wanted to meet me again. But it's hard to believe that sometimes

It just makes me sad, because for all I know, he's living it up sleeping with guys and ignoring me, meanwhile I'm here hoping for more.