I am a student studying in the final year of highschool with a huge and important test coming up year end. Apparently I have noticed a classmate of mine that always seem to be down in drains. So one day I decided to help him out as we weren't particularly strangers, I walked up to him and I asked him what was wrong and listened to him patiently. Turns out he was an extremely sensitive person that really cares about people's judgement and gets sad everytime he feels that he isn't doing good enough. He felt much better after talking about his problems.

But here's where the problem start, a few days later he asked my desk mate to move away so he could seat right next to me, knowing he was very sensitive, my desk mate obliged. The first few weeks were fine, we had a few deep conversations and cracked a few jokes along them. But then it started to get out-of-hand from there, he won't let me talk to other people and feel real sad when I left him. Everytime I talk with a few friends, he drags me back so I could talk with him. He follows me everywhere and overwhelm me with his negativity and pessimistic views about life. I mean I get that he is sad but he is almost basing his entire personality on the fact that he is sad. 

But the real frustrating problem is he keeps bugging me during class. As I said I have a huge test coming up, but this dude keeps cracking unfunny jokes in between that really is a distraction. I told him to stop but he just gets all sad and negative about it. So after an entire month of that, I decided to ignore him for a bit. I moved seat because I have decided that my own wellbeing is the priority but everytime I catch sight of him in the backseat, looking so damn sad and alone, I can't help but feel guilty about it. AITA?