PMS or pregnancy

I was just looking at my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> calendar and I've noticed my periods usually begin every 18-20 days but in December it began in 24 days. It was very light. My boobs/nipples are so so sore and for the past week I've been having menstral-like-cramps that goes on and off. I've also haven't been having an appetite and I've been urinating a lot and been having acid reflux. Could I be pregnant or PMS?