Just curious..

Erica • I`m 25 years olds. Have been in a year n half relationship with my boyfriend that I live with. We don`t want kids yet.
I just started using Glow. I  am now 2 days past when glow said I would get my period. Is it normal for glow to be off on what day I should start? Or do I need to be considered? I haven't been feeling very well lately. So now I'm panicking.