What causes stuttering?

What causes stuttering? I'm 14 and i started stuttering when i was 5, but than the stutter went away all the way up until i was 10, that's when the stuttering came back again and i still stutter today, my dad keeps saying i will outgrow it but i don't think that's gonna happen if I've been stuttering for 4 years now. how can i make this terrible mental problem go the hell away and never come back? My older siblings call me slow and retarded and it's not my fault my speech is fucked up. How can i solve this atrocious ilness? Is there any medication i can take for it?