Need opinions...

I am always on schedule with my period, which was due the 8th. It is not here, but every preg test has been negative. Did not use ovulation sticks, but I was supposed to between jan 18-23; had small brown spotting on jan 26th - I assumed implantation as that also happened with my daughter. I did get positive tests with my daughter, but I didn't test until I was 6 weeks. Any ideas about what is going on? Obviously too soon to call my dr. Urgh.