(skip to next paragraph to not read my rant if you want)
Bullying eh? I use to be the center of attention with any fat-related jokes so everyone literally saw how 'cool' it was to do this and threw out verbal abuses very casually. At least your situation is only because of one dementedly troubled kid. One day, I literally snapped and a long story short, I've heard much less of these jokes during my last year or two in elementary school from my classrooms and other people. There might have been other jokes like about my parents, but the fat ones were the ones I most vividly remember except for the details. Middle school was a time period of more fights for me than slangs/slurs whatever you want to call it although those were thrown to spark off tension. One of the main reasons I could care less about my elementary and middle school years besides how bad education was back then.
Anyway, you have a few solutions. For one thing, you could try befriending the one(s) who are picking are you. It worked out surprisingly well for me, and I ended up having some close friends after we resolved our differences and worked it out through a mutual understanding with one another over time by talking about it and getting to know one another. Right now, from what I mostly remember of them wasn't the bullying but fierce games of dodgeball and fun we had hanging out. We would still joke around though but name calling between friends is easier to deal with than hearing it from strangers, right? I believe since people eventually saw me with a group of friends, they tended to lay off of me. Although it could just be my imagination, it just seemed too much of a timely coincidence.
If that doesn't work, depending on how 'influential' your school is, I would heavily suggest talking to the counselors and such and inform them of the current circumstances and see what happens, which you've done. Sometimes you have to pray how lucky you'll be when he confronts you and hope there's a teacher or adult around to witness the event. I still recall the time I received a death threat in middle school on the basketball courts. I ended up telling the school officers soon after that and days later when we had that fight in front of the school, guess who ended up winning the war?
Thirdly, you could consider avoiding him but because of how unfortunate you are and how your paths end up intertwining sadly, I say avoidance is an option waiting to fail but that doesn't mean you shouldn't take steps into trying to be nimble. Try taking a different hallway, alternate between staircases and so forth from time to time to getting to your classroom to simply avoid meeting him altogether, even if it's for a moment, Don't let him get to you. Sometimes having 1 minute to yourself to relax and think while going to your next class is a nice breather. The last thing you want to do is retaliate and be seen as the aggressor and then all the blame is put on you for first starting it but since you've had prior cases where you've reported this abuse, it could work to your favor but I wouldn't count on it. The school's disciplinary system can be quite murky and weird most of the time although those of my memories of it so I wouldn't know how it is for you at your school.
But if it's in the spur of the moment, sure, why not? Fight and let it out but never be the one who sparked it first or you could be seen as the one who wants redemption when clearly you've been suffering all this time. I was fortunate how my situation ended up resolving since my classmates confessed about the 'incident' when I snapped and what exactly happened, I was off the hook.
And you are a guy, right?
The Grim Reaper said:
There is something I haven't told you guys. One time, when I got off the bus, he asked me to let him do me a sexual favor.
All the more reason you should have reported it to your counselor or a school official immediately. Something as severe as that CANNOT BE SIMPLY IGNORED, even by the school or they aren't doing their jobs and will be liable for the consequences you are faced with.
The best thing I can see you doing is simply talking to him and start questioning his motives and agendas or anything you feel like that won't spark too much passion from him like some have said already. Ask him directly or indirectly, depends totally up to your personal discretion since you know his habits on when he picks on you, what he has a tendency of doing in a certain situation when he mocks you and so forth, on how you want to approach him. Be witty, confident, and above all, have an intrepid bravado. Since he's picking on you, why not talk back at him? Some bullies I've encountered have a fragile mentality when questioned casually. You did mention you've talked to him at times and he merely shrugged it off, but you should try to encounter him in a conversation for yourself only when he confronts you like in class if he repeatedly seems so adamant about engaging in one since he desperately is craving for your attention. Having confidence and standing up for yourself is something you shouldn't be giving him the benefit of demolishing as you'll only be feeding him his superiority complex he feels every time he tortures you.
If talking to him isn't your thing, don't even give him a response. You're only feeding his arrogance by doing so. If you must reply, then do it without giving him the opportunity of giving a strong response.
And I quote...
in the end, fighting is not worth it, just ignore them, push them away, laugh them off. Unless they are physically harming you or your property, don't even bother with them. if they are, tell someone first. if that doesn't work (and often times i understand that it doesn't. In schools you can't really get to other children through school discipline anyway), try to find some way of avoidance, and if it comes to it, punch them good in the face. but only as a last resort.
Unless he's utterly beating you up after school or on the bus occasionally, I'd simply play ignorance and leave him be since it sounds like the most he has ever done is like throw paper balls at you, spread horrible rumors and verbally dissed you or whatever. No matter how annoying he is, unless he does something so outrageous that warrants a response from you with no other alternatives like asking you for sexual favors that make you feel like yelling blasphemy or something against him, then do so.
And quickly report about this sexual harassment. That's simply too far even for you to bare alone.
And what about your friends? Try sticking together in a group with your friends to ward off his presence or participate in a after school activity by joining a club or something to free yourself from meeting up with him so often. If you still surprisingly encounter him even after practice at 6 when school ends at 3 everyday for you for example, then he sounds like a stalker...