Help!!

my period was supposed to come July 25. it didn't show up until August 8th. the doctor told me it's normal to skip a period. I'm bloated, moody, some cramping, nauseated. I've taken multiple pregnancy test they were negative are my hormones just out of wack or what? I have two children usually pregnancy test would come back positive but this is just weird. We are not trying but I know what God has promised me. Every promise he makes shall come to pass. Answers??? Help!!! please and thank you.