Hi and thanks for the query,
the commonest cause of delayed periods or lack of periods in a female of reproductive age is pregnancy
. The fact that you had risky sex makes this possibility very valid, A good pregnancy test is there fore well indicated in this case. However, in certain woman, there are cycles called anovulatory cycles, not accompanied by the release of egg cells, that might be associated with delayed periods or at times no periods. But excluded the possibility of a pregnancy in your case is very important. Doing a good pregnancy test, especially with use of blood samples to measure the Beta HCG
levels shall give almost conclusive results and guide further management options.
Thanks and best regards,