Dear 16 Year Old Self,
You are incredibly strong and smart for seeing a therapist to deal with some of the ex-related bullshit. You should come out to your parents as soon as possible. You know they'll be supportive, but don't worry about the "finality" of it, it's just accepting the finality of who you really are.
Be proud of who you are, no matter what happens in the next year or two. It's going to be shitty, but Mom's going to beat cancer into an oblivion.
Don't beat yourself up too much about your social life. You're going to be an extrovert at times, just not all the time. If you pick the right college like I did, it's going to work out beautifully. You'll make a lot of friends right away and stick with some of the absolute best ones.
Start running every day now, it'll make high school so much more bearable. When you get to college, watch the empty calories from alcohol and the dining halls.
Nobody ever gets it all figured out. We just keep rolling with the punches and try not to repeat our mistakes.
Oh, and also, don't worry about McCain/Palin, Obama's got this one easily.
20-Year Old Self