Can i be pregant???????????????

Hi im 17 and i had almost a month ago. me and my boyfriend didnt use protection ( i kno bad right) he pulled out so i know he didnt come inside me (he's to scare to anyway). but ive missed my period i do have a irregular period though. i took a test yesterday and it came out negative, ive been under lot of stress abd stuff. if i was pregnant i would be bout a month but i dont show no signs...............could i be pregnant????????