Even though headaches are a sign of pregnancy that alone should not be reason to suspect you are pregnant. Hormonal changes in the body early on in pregnancy can increase blood circulation which can cause mild headaches. If you are prone to headaches becoming pregnant sometimes can make them more severe. For most women headaches will stop or become less frequent by the second trimester. This
. symptom along with others such as tender breasts, fatigue, cravings or nausea, moodiness and fatigue all can be signs of pregnancy. You can find more information here: http://www.americanpregnancy.org/gettingpregnant/earlypregnancysymptoms.html