Helpppp, advice, something pls reply !

Okay so not to long ago.... probably about a month ago my sister came to me saying one of her “brothers” can’t stop talking about how “beautiful & pretty” I am & that she thinks he might want to get to know me so just to be open about it . The boy ended up communicating with me that he had an interest in me & that in-fact he did want to get to know me so I would say things like “oh okay” cool I’ll think about it you know I would deny they hang outs & tell him I was still thinking about it for the simple fact that I’m an observer & will watch how you interact with others and w/ me similarly or differently. From what I gathered up about him is that he’s “playful” I guess you could say . He would play fight w/ other girls and I would over here him and his friends talking about how fine another girl was .... I ended up turning him down . He wasn’t to happy about it he went on to “bugging” me I guess you could say and was consistent w/ asking me questions and to hang out or for hugs etc. I ended up making a post later on a few days later asking for “some cool people who were looking for friends” & he said “hey new friend” that’s where it all began ...... we ended up talking literally EVERYDAYYY ALLL DAAYYY !! He told me how I was the only girl he really was trying to get to know this school year & how he didn’t want anyone else he honestly would just waste time with the others who never pushed me to kissing him or having sex or talking sexual etc. We got to know things about each other and we’re happy with it & I actually started to like him in that short period of time that consisted of about 2+ months we started to argue or have “disagreements” I guess you could say & most of the time it would be me saying things like oh wow I see how you were flirting with so and so which lead to him saying how he doesn’t owe me and kind of loyalty...... few weeks later about 2... one of my close friends called and asked if I talked to him by then I was confused by his actions and everything USSS so I said “no not anymore, we kinda did it’s complicated & he’s weird. Why ?” She went on with how he was in her inbox and wanted to talk to her . 🤦🏽‍♀️ I said “yea whatever go head if you want to ima warn you he’s weird tho, play your role or play him idc .... I never thought she would go through with it ! But she did I guess and throughout them talking he would still be in class asking me for hugs, sitting next to me, touching me, telling people in class we were together etc . My friend just told me how they got into an argument and how he ended up telling her that he just wanted to have sex with her how he only really wanted one person and that was me and that they’re done he blocked her on everything & I just noticed he’s been on my page liking old pictures, commenting on my post and constantly inboxing me I keep leaving him on delivered etc .

I just don’t know what to do I feel like I should leave him & her alone because one she still went and talked to him after I told her I talked to him. I would never do that to her even if SHE told me to . And him HE KNEW she was my friend and went for her .... what should I do ? 😫