Confused.

Beth • Mammy to Phoebe after waiting nearly 3 years. Worth the wait💜 13.09.19 7lbs💜
Does anyone know why glow says I only had the 19th and 20th fertile days last month? I also bled 2-4th January but possible chemical. Glow says I'm due on 31st. However, my other app says I'm on my 2nd day late. I need some help, please.