You are brave and courageous for talking about these very uncomfortable thoughts and feelings. The fact that you feel very uncomfortable about these thoughts is a good sign. It is really unfortunate that your parents are not understanding how difficult this is for you. I would ask them again, perhaps even show them this column, and see if they can set you up with a therapist. These thoughts can happen for a variety of reasons and getting to talk to a therapist is a good way to get to the bottom.
If your parents won’t help talk to your school guidance counselor. He or she is in a very good position to help. They have specialized training in helping young people through these difficult periods. You can also show them this column.
Wishing you patience and peace,
Proof Positive Blog @ PsychCentral