If your temperatures are erratic, the first thing you should do is review the guidelines about taking your BBT and make sure you are using a special basal body temperature thermometer. If you are following the guidelines (taking your temperature at the same time each morning, before getting up and using a BBT thermometer) and still have erratic temperatures, review your data to see if anything in your environment or your habits could be disturbing the temperature. You may also consider changing your thermometer or replacing the battery in your thermometer to see if this helps.
Some women who are unable to get a clear pattern when taking an oral temperature are able to get a clearer pattern when they take their temperature vaginally. If you have several cycles that are erratic and you are taking and recording your BBT properly, and you are unable to see an ovulation pattern, you should talk to your healthcare provider.