I dont know if im pregnant...or just late.

Hi everyone, i have a few questions, im gonna be 20 soon and ive never been pregnant. my period is usually irregular, basicly comes when it wants. but usually around the beginning of the month. my last period was the beginning of december. I did start bleeding but only for a day at the beginning of this month. sometimes my period only lasts a couple days. but my breast are very sore, ive been alittle tired lately, and somedays i cant stop eating, nothing strange just normal things i eat. ive also been having cramps lately and i feel swollen. ive been preety moody lately too. my mom thinks im pregnant but i dont know if i am. is it possible that im pregnant? or could my period just be very late due to stress? also i took 2 tests, and it looked weird. it had a very dark negative sign and another line to but it was hard to see. both tests did that.