"literally right before" your period isn't 11 days before. You can absolutely be pregnant. Give it a few days, test again. If still negative and no period go to the docs for a blood test.

You can get pregnant before your period as you may have ovulated later than you thought. Even if you are always regular, you never know if you are going to have a month where you ovulate late. Ultimately if you don't want to get pregnant, use contraception at all times. Also if you have ovulated late, your period will be later than usual if you aren't pregnant, so give it another couple days and test again if it hasn't arrived.