Thank you for your question.
Most women will have missed a period or two at some point in their reproductive cycle. Other than a pregnancy, there are several reasons for period cycles to change. Sudden weight gain or loss, thyroid disorders, stress, change of job or home, relationship stress, change in dietary habits can all contribute to period changes. You are correct to do a pregnancy test first. You can wait two weeks before repeating it if your period still does not come. If that is negative as well you should see your gynaecologist for further tests and medication. Please use reliable contraception in the meantime if you are not planning to conceive