Try taking one more test, with a couple more days. If you're really nervous, go to the doc to get a test. And while you're at the doc, ask about the weird cramping.
Did you take any EC (emergecy contraceptive)? That always screws with the functions. If not, I'm sure it's the body just reacting to the hormone craziness.
Now...WHY WERE YOU HAVING SEX WITHOUT PROTECTION!? Don't do that! Have something! Do NOT do that again! Condoms are free some places...and others, they cost $6...pick up a pack and keep them in your purse! Get spermicide ones...they work wonders!