Kindness?

My entire school career I have spent my own time in and out of school trying to do any good I could. But this week I have had a really hard time with being treated terrible by people I have gone out of my way to help. My friends ditched me, talked bad about be about 5 feet away from me, and just completely used me. I just couldn’t take it anymore and had a total breakdown when I got home. I have had so many friends and I always end up getting manipulated and used by them in the end. My mom has always told me when doing the right thing and being kind you shouldn’t expect a return but I don’t even get like a thanks anymore. In fact people are meaner to me now. One of my best friends has Down syndrome and I spend lots of time with her and I get made fun of it for it. My mom is like my best friend but now I feel that she doesn’t even understand. I just have had a really hard week with people just completely using me. I feel like I can’t do anything right anymore I reported a kid for cheating and the next day he was in my face threatening me and cursing at me. I just don’t know what more I can do when I do good all I receive is bad.😔 I just want some other opinions on what I can do.