This guy friend is getting too much

He's a friend, were both 22, and in the same college we have the same friends and we're a part of a group together. On some days off, I can text him, but he expects me to be glued to the phone to give him answers to his questions- I should enjoy my own time after telling him, if I don't reply within 1-2 hrs he started texting "Are you ok? What's up? Why aren't you texting? You're checking the group mesages but not mine why aren't you responding?" He did the same to his girlfriend and he calls me his sister but he's subject me to the same torture. I don't think I'm close with him. Despite how much we've talked, it's all been more of giving and less receiving from him. In some good days I respond and stuff but on other days I withdraw but it calls for his immediate reaction and it's a series of 20 messages for 2 hrs atleast till it's too much and I tell him that I'm not answerable to him 24/7 about my activities at home.

I'm so tired, I just came back after telling him for 5th time this year that he has serious victim mindset and abandonment issues. It really makes me want to block him, I will block him think. Very soon. I'll graduate in May. Why is he doing this to me? I feel so drained after talking to him he says nothing of value, useless talks that he wants me to do all day I do it sometimes when I'm lonely too but he's been obsessed to the point that I don't want to explain myself and I don't want to tell him the answers, rotting in doubt might help him create it.