What to do about stalker/obsessor

Hey I’ve been needing some help and have been asking a lot of people on what to do.

So I’m 17 and am a senior in high school. In September school was going okay. On my first day of school I had some issues with people in my English class so I switched out as fast as possible (which ended up being in October). Anyways, there was this guy in my class let’s call him James. I didn’t notice James at first until he started talking to me and sitting next to me when we would go to the computer labs during class. One day he randomly looked me up on Instagram and I let him follow me. He didn’t become stalker-like instantly but it developed over time. I didn’t know this same guy was also in my Econ class. He started sitting at my table and I thought nothing of it. I started to date one of his best friends and during the 3 month relationship we had, James was always trying to get me to brake up with my boyfriend so I could be with him instead.

The past month or so after the breakup, James has literally been obsessed with me. If I leave him on open on snap for less than 2 minutes he will continue to Snapchat me until I respond. He constantly tries to call me and wants my attention. I’m at a point where I don’t know what to do. He has always made me feel uncomfortable and I have told him multiple times that I’m not able to hang out after school with him or I can’t hang out during the weekends and things like that. He will do anything to be able to see me or he will want to do anything for me so I won’t have to do it and has said he has a “crush” on me. I started not opening his snaps and I blocked his number and Instagram.

He still has class with me tomorrow and I’m not sure what I’m doing to do. He still snaps me every 20-30 min making it over 20 snaps a day from him since Friday, when I haven’t been opening them. When should I go tell someone at my school and how do I tell him I’m not interested again because I’m afraid this will never stop. Any normal person would know that I’m not interested by now and if I’m not responding, it means that I want to be left alone. I’m just really creeped out and his behavior is extremely inappropriate for any “normal guy.”

Sorry this was so long but I would appreciate some advice. Thank you ladies 💗