What Causes Delayed Periods?

Hello... I have had dry sex with my boyfriend before 20 days with all our clothes on.. We have been careful there has been no other way physical contact.. Now u have not got my periods since then.. Its 5 days past my date.. Menstruation has been regular throughout till this time when it has been delayed by 5 days.. Am worried, could I be pregnant..? Also to mention I have been taking treatment for hair fall and alopecia since 10-12 days, some of which r nutritional supplements.. Can they delay menstruation? Please reply...