Pink-ish Discharge

So my last period was from the sixth to the twelfth of this month, and I have irregular cycles (I went all of April without one). I've been in a relationship for over a year, and we're pretty sexually active, but no protection. I'm not on birth control either. So I went to the restroom earlier today and noticed a pink-ish discharge in my underwear. Not a whole lot at all. My next period is (according to this app) supposed to come within the next week or two, I believe. I'm trying not to think it's pregnancy, so I just wanted to ask what everyone else thinks it could be? Thanks!