Symptoms? period vs pregnancy

Do women often get period signs and early pregnancy signs confused? My period was due today but it hasn't started. I thought maybe it was going to due to slight cramps (I never get bad cramps) the other day. I've been off and on nauseous with pretty annoying headaches. My period is usually on time - maybe varying a day or two at most. Thinking of buying a test for tomorrow morning but I don't want to get my hopes up.