Have anyone tell you that they masturbate for you?

Yes, a few boys from the same group it was when I turned 16 … they told me that they do masturbate and they do it in my name. I feel so embarrassed coz they told me this in front of me. They didn't do it intentionally … they were just discussing as boys do and I went near them and was listening to everything once they noticed me then repeated the same thing with a sorry…. I was like what's going on then I asked them how they can masturbate in my name they simply replied to me that they assume me naked and start thinking about having sex with me. Then I ran and left that place I was feeling so unsecured. Well, now it is like a funny memory for me. The sad part is we are not friends now and didn't meet them for a long time