Possible Pregnancy, medical advisers

I have had irregular periods since I was about 11 or so. Now that I am 20 it's still irregular. Sometimes it'll act as if it's regulating itself, but will just mess up again. Any suggestions to help regulate?

Anyways that's not my actual concern, lol.

I have protected sex sep 19, 2014, I supposedly ovulated 8 days before. I had what was my period that month, it lasted 10days. On the 21 of Oct I spotted, then on the 22 I had cramps(which never happened before) 23 the spotting stopped. My period was suppose to come the 24 of Oct but didn't. I took a pregnancy test on Oct 28, 2014 and tested negative.

Is there a possibility the test could be correct?

Can I get pregnant in this scenario?