NINE POUNDS IN A WEEK!@# 9 POUNDS! Help!@#?

Ok, so here's what happened. Oct. 31st I lost my virginity, the condom slipped off. And I had to go get the Plan B pill. This caused me to bleed on Nov. 5th, I'm guessing as a period, or as a side effect to Plan B. Either way, on Nov. 23rd, I started on birth control (Ortho Tri Cyclen Lo). Today on November 30th, my weight is up by 9 pounds. I have not had another period due to all of the hormones that I've ingested, I feel almost sicked that I have put on this much so quickly, because I worked my *** off to lose 85 pounds over the last year and a half. Is this water retention or actual weight gain? OH. And P.S. I'm a cashier so I'm on my feet all the time burning calories. I just started my job as well, so I have been a little bit hungrier. But there is no way that I've ate enough to put on NINE pounds in a week. PLEASE HELP!@#