Most probably you are not pregnant as you had a period at the 15th of March and no intercourse occurred since then. But because you are scared and to be sure, you should have a quantitative pregnancy
test in order to rule out pregnancy.
If the test is negative you may either wait for spontaneous menstruation
(you may wait upto 7 days more), or you may visit your doctor to prescribe you a drug to induce menstruation.
I hope this piece of information was useful to you and I am ready for any other questions.
Dr. Ahmed Bahaa.