I am on combination pills and I happened to miss 2pills(I took them as soon as I remembered) on the first week of that pack. Some hours after having unprotected sex with my boyfriend I decided to take plan B. The lady at the pharmacy asked me to discard the current pack of pills and start a new pack, which I did. 2weeks later I was supposed to have my period but I am 4days late and don't know when I'll have it. Is it because of the plan b or the new pack I started? Is it a cause for concern?