What signs do you get before your period?

im 12, have had my period for about..2 years and a month (i guess), and ive been getting different signs that my period is coming each time. 3 periods ago, i had headaches. 2 periods ago, stomach aches. & last period, i had some little cramps (i never get cramps). i usually get those DURING my period...& i never got signs before, but lately i have. and the symptoms have just been varying, and i wanna know what i could expect. so if u could lemme know any of your signs, that'd be great :]