Hi there im sorry to hear what has happened to you. The stress of your aldeal may be the reason why your early, as each woman's body reacts differently to shock some have a delayed period others have spontaneous bleeding. Some of the medication you have been given may flush your system, if you are concerned then i would recommened that you see your doctor and ask what the medication was for and why you were given it,they will give you an indepth explanation.
The main purpose of PLAN B is to induce your period so yes this could be the reason why your period is so early. Speaking from my own personal hell i'm so sorry you had to go through what you went through if you need to talk at all i'm here for you and believe me i understand if you don't want to. stay strong girl you'll get through it. all my prayers Becca