im 20, and my father died 3 weeks ago

I called Dad on January 21st on my way home from work and he was completely fine-- happy, laughing, talking so excitedly about how he's finally put a deposit down on the jetski he's always wanted. The next day, my mom called me very late at night asking me if I was at my apartment. I would have never expected her to knock at my door, sit me down on my bed and tell me my dad had a heart attack. He was only 55. He wasn't the world's healthiest man by way of eating, but he never smoked, barely drank, and was so active-- he played on three different local softball teams and was always out on a walk somewhere. The only health problems he had beyond being a bigger guy were sports injuries. But I guess none of that matters now.

I'm only 20, and I don't know what to do with myself. I'm in my third year of university, but can't bring myself to go to classes. Most of my professors don't even know my dad died-- I can't bring myself to send the email. It feels too real to do that. I've missed multiple exams and can't bring myself to do anything about it. None of my friends know how to talk to me, and I don't blame them. I'm the first person out of anybody in my circle who has had to experience a loss as profound as this. I am glad they don't know this pain, but I wish people wouldn't pull away because they don't know what to say. I feel so alone out here, grieving a loss I was not supposed to experience this young.

I loved my dad so much. I wish I spent more time with him. I wish I told him I loved him more. I wish I had given him more hugs. I wish I played ball with him more. I wish I answered the phone every single damn time he called me. I wish, I wish, I wish. So much left undone, so much left unsaid.

I just want to hear from people who get this feeling. Whether you are my age or eighty. I am hurting so much and nobody seems to get it. Not even my family. My mom divorced my father 10 years ago and is remarrying this summer and has gone back to living as if nothing has happened. My brother was not close with my dad and has done the same as my mom. His girlfriend is reeling, but it is so hard for me to be around her as she is the one getting all of the love and care after his death while I have just been expected to cope because this is what happens to everybody at some point or another- everyone's parents die. It's all so unfair. I am so sad. I just want someone to hear me. To witness my grief. I don't know.

Thanks for any responses any of you leave. I appreciate you even reading this. I loved my dad so much. He was such a great man. No other way of putting it. He was so special.