Help anyone

Lucy
According to my calendar I was suppose to get my peiod on the 26 in 2 days late . But my periods are irregular . 
I got my period on the 1st of this month and ened it on the 5th . Since then I've had unprotected sex mutiple times through out the month espixally right after my period . My periods are short some I'm so irregular and only have my period up to 3 to 5 days . 
I took a test a week ago and it came out negative , I'm guessing it was to early so I'm planning to wait until the 1st or 2nd week of October? Can anyone help me and explain it to me ... ?? Can I be pregnant .