Delaying my period?

Stress may delay it but I don't think that is going to help you. You can still have when you're on your period but it will be a little messy. Since this is going to be your first time I would just explain to your boyfriend that you started you period and would prefer to wait until another time. You don't want your first time to be a bloody mess. If you're certain you are ready to have then you can wait until the time is right.