Hello dear, If you are sure that there is no entry of sperm inside your genital tract, then there is no chance of getting pregnant. However, as you are worried, you can use a home Pregnancy test Kit. In case of Pregnancy, it will give positive result within 1 week. Causes of delay in periods can be many such as infections, anovulatory cycles, hormonal imbalance, stress, anemia, any pathology in the uterus, ovary, etc. So, it will be better to consult a Gynecologist & get a proper clinical examination done. Investigations like Ultrasound scan of the abdomen & pelvis will be helpful. Wishing you a good health. Take care.