Well i must agree that if it says positive ...it will generally mean you are pregnant. As long as you didnt read the test after too long (as sqiffy says).
My guess it that you are pregnant. Was your last period regular or just light spotting. Sometimes people mistake a light period as a period when it is spotting so you may actually not be testing 11days early but testing later. (if that makes sense). Was the line on the test a dark line? because if so it may confirm my theroy. Preg. tests pick up the HGC evls in your urie which are only produced by the body when you are pregnant.
Best thing to do is to go to you doctor to get a blood test done. These are very acurate
Best of Luck
Annabelle