It sounds to me like your dad has a lot of himself invested in making sure you're the one with the "problem," so he can feel better about himself. When they talk about your older siblings being "out of their control," they mean, "living their own lives, instead of doing what we say all the time." They no longer have a say over your adult siblings, so they're doing everything they can to control you to death.

Do you have a school counselor you can go to? Being in therapy may in one way play into your father's hand. "See? I told you you're messed up, and that's why you have to see a shrink." I know, my family played that game with me. They made darn SURE to rile me up emotionally as much as they could, so they can tell me I'm crazy and should see a counselor. But in reality, it's the ones in the family who are *most* normal that get the help. The rest, who think they're just fine the way they are and it's the whole rest of the world that's messed up, don't know enough to get any help.