Other thoughts that I would share with a younger me:
On the list of "future kid names:" Kimberly is a perfectly nice name. But "Kymber Lee" is a bit much. Naming twin girls "Brooklyn and Brittyn" wouldn't have been unique. (Also, there are zero instances of twins in your family, so it probably isn't necessary to plan for them.) And there is a 50% chance you could have a boy, so you might want to consider male names as well.
On the German exchange student: Instead of being upset that you weren't selected to be on the Homecoming Court, be a little more gracious to the German exchange student who asked you to the game and dance. He is actually pretty cute and very nice. And he bought you an awesome mum. And he paid for your chicken crispers at Chilis. It wouldn't have killed you to befriend him for the remainder of the semester.
On mom having breast cancer: Go see her more often. She has CANCER and she only lives 20 minutes away. You are not THAT busy. You could go to class, run over for lunch, then go to work. You're lucky she beat it and you don't have to regret the time you didn't spend with her.
On "Saved by the Bell" and "Beverly Hills, 90210:" Totally worth watching. But if you missed anything, their reruns will live on in eternity.
On "those" girls: The ones that are prettier, skinnier, richer, funnier, better dressers, exude confidence, are more articulate, more polished, more WHATEVER. They are going to exist in some form or fashion for the rest of your life. You are enough. And the moment you finally believe it will be life-changing.