most girls do that from what i hear,,i think its just your cycle.. it wont be like the first week of every month.so no nothings wrong with you.. its normal
Your body will regulate itself, it may be regular for you to be irregular, everyones cycles are different, most fall in the "range" of 28-31 days many do not. As long as your not bleeding excessivly or having increadibly unbearable pain its ok.