How accurate is Glow period forecast??

I had very light spotting yesterday. Today, a bit heavier but still no flow (just when I wipe). Period isn't due until 22nd according to Glow but my periods are pretty irregular. My husband and I were TTC the past couple of weeks, wasn't ovulation or in my fertile week, but then I realized I had only recorded my last cycle. When I input the rest, it pushed my period back a ton and my ovulation. So.... What does everyone think? Took a (negative) test yesterday. When should I test again??