1. I'm pleading guilty, so I don't need an attorney.
Always consult with a defense attorney before making your move. You want to assess your options that may be available to you.
2. I can't be charged with DUI if I'm under the legal Blood Alcohol Content (BAC) limit.
3. I can't be tried more than once for the same crime.
But the Double Jeopardy Clause does not prohibit a federal prosecution after a state prosecution and vice versa.
Also, Double Jeopardy does not firmly prohibit retrials. For example, Heritage.org states that the "clause is no bar to a new trial when the defendant successfully appeals his conviction, but a successful appeal of a lesser charge (manslaughter) by a defendant precludes a retrial on a greater charge (murder)."