Late period?

Ruby • Live, love, laugh ❤

Why is it that glow changes the date of when my period should be here I was due on, on the 15th but nothing came so I pit period late. It then expected me to be on two days later (17th) it didn't come so then it expected me on todah nothing so then now it's changed it and I'm apparent due on on the 20th.

But how is this? I always have a 28 day cycle?

I misscarried last month and even Dr's said I'd be due on on the 15th