How do you know if you are bi-polar vs. another mental disorder?

im 13 and im kinda like that except the bulimic part im muscular i have a bad anger problem im always thinking of killing people or myself i cut myself somtimes but no one thinks there is anything wrong with me my brother died i didnt shed a tear i didnt care at all i still dont i dont feel bad for people but my advice is to go talk to a school consoular or doctor or just a good listening friend who can take it seriously i wouldnt talk to my parents personally because my dads a douche and mom is just wierd to talk to with this kinda stuff hope i helped