Late?

So all my apps say I am supposed to start on the 19th and when I didn't start glow moved me back to start on the 25th so I'm thinking I'm two days late and I'm never late took another test this morning and still negative but with my first I didn't test till 14 days after my missed period and only a very faint line? Has this happened to anyone did u just continue to test until you got your positive or your period?