I'm Lost Without Him

I'm Jennie and I'm 14 years old.
When I was in year 7, I had a mate called Karl. At the end of year 7, Karl moved and I never saw him again. About 8 months ago, someone called Karl added me on Facebook. I said to him ''Do I know you?'' and he replied ''I thought i recognized your name... sorry if I'm wrong''. I talked to him about my school (which he seemed to know a lot about) and he talked to me about where he lives. About 3 months past and I truly thought it was Karl who I used to go to school with. By this time, we are madly in love and he asks me out. I obviously said yes and so we had our relationship. About 4 months pass and (because I'm only able to talk to him over the internet and by phone) he tells me he is 17. I am gob smacked at this but I say nothing. My brother gets suspicious of my relationship with him and decides to message Karl (which I asked him not to) and he tells Karl that in 14, I don't have true feelings for him and that I lied about everything to him. The next morning, I get a text from Karl saying
'' How could you do this to me? Why would you do this to me? I nearly died because of it.''
This upset me terribly and my brother leaves me a horrible voice mail on my mobile which makes me cry. Then Karl talks to me on MSN and says that he isn't angry or upset with me, he is just confused at to why I didn't say anything... so i told him everything. He forgives me but doesn't want anything to do with me anymore. And all I have now is my brother leaving me really horrible voice mails which is killing me inside. I don't see how I can cope anymore... I've cut myself and I've cried as much as I can... but it doesn't do anything.
Please help me
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x x