Period is late according to Glow

Hannah • Endo Warrior 💛 Wife 05/16/15 💍 Mommy to Aurora Jane 10/09/17 our rainbow baby 🌈 and mommy to one angel. Pregnant with a boy, Oliver James due 11/8/19
Period is late according to glow. And I am having a dark brown discharge in my underwear. Not normal! Also have taken two naps today, and am constipated and gassy. Thoughts? (Can't buy a preg test till Thursday. Actually have a gynecologist appointment on Monday for unrelated reasons)