Chemical Pregnancy?

Lizzie • Baby #1 "Smalls" 10/13/15. Baby #2 due 04/15/19
Hello, 
Has anyone had a chemical pregnancy? I got my BFP on Sunday. My AF was due today. I've been cramping and am so worried it was a chemical. No bleeding but the cramps feel the same as PMS. If I retest today will it be accurate in telling me if I am pregnant? Also another app said my period was due 1/29. From my last period this app said I am 4 weeks. Help! First time mom freaking out.