You may have received a negative test result the second time due to excessive liquid intake.
You should test at approximately the same time each day. The best times to test are between 11am and 3pm and 5pm and 10pm. It's best to reduce your liquid intake for two hours before testing because drinking excessive amounts of liquid can dilute the LH in your urine.
You may also want to use a Basal Temperature (BBT) Charting Tool, like the one found here , to track your cycles.
Good luck!
