Period a year after baby

I just had my son 10 months ago. With that being said I've had a period every month since he was 4 months old. I'm currently breastfeeding, so I know that can mess with your cycle, but I'm 4 days late. I've had unprotected sex, but nowhere near when I was supposed to be ovulating. Should I take a test or do you think it's because I'm still breastfeeding and that's what is causing all this?