Help!!

I'm 12dpo and been having cramps in my lower abdomen and they're getting worse and been feeling quite nauseated. Took a test, and it was a bfn. I want to hold off going to the Dr until next week when AF will supposedly arrive. Any idea what's going on with me, it's the first time this is happening for a long period of time. Could I be pregnant? Or is something medically wrong?