Thank you for writing. Your letter is not a “jumbled mess”. It is an articulate statement of very difficult feelings. Please listen to your dad. I know you know he’s right. You do need to reach out to someone. I also know how difficult that can be. The paradox of mental distress is that just when a person feels so stuck, the way out is to take the first step. In your case, it means making an appointment with a licensed mental health counselor who can help you determine what is wrong and make recommendations about how to become more comfortable in the social world.
Your letter is so well done, it can be a big help. Bring it to the first appointment or ask if you can mail it to the counselor ahead of time. Then you won’t have to explain what’s so painful to you on the first meeting with a stranger and the counselor will know where to start.
My guess is that things have gotten worse since you graduated from high school because the familiar faces and familiar routines helped you feel comfortable. Now that you are in college, you’ve had to start over. Please don’t scold yourself for feeling so distressed. Many people go through some version of the same thing when they have to deal with a new social environment. A positive side to this is that the change highlights the issues enough that someone like yourself faces it and gets the help they need.
I wish you well.