To worry it not to worry.?

So this says my period was supposed to come on today but nothing. Im kind of lost my head has been in pain ive been very irritable and hungry. Its hot as ever outside and my bestfriend,who is pregnant, swears she think I may be pregnant. I dont know what to do. Its only one day cant be to serious right.?? I mean yesterday I spotted very light then nothing thats it. I'm lost and am umclear on what to do.