2 periods in a month?

I was stupid and drunk 3 weeks ago and used the pull-out method I got my period a week later and it lasted 5 days so I assumed I was in the clear. However today I started cramping and bleeding again like a 2nd period 16 days after my last one began. Could I be pregnant? Or is it just stress/irregular period because I have a history of irregular periods. I have gotten 2 before in one month about 2 years ago.