A few weeks ago I stopped taking my birth control mid pack (October 13 was the last time I took a pill... I know that was bad to do; I was going to wait until the end of the month but forgot). A few days later (October 15) I had sex but the condom broke. I took Plan B 15 hours later as directed.
I know that stopping BC, especially mid-pack can mess up your cycle; if I had still been on BC I would have gotten my period last Tuesday (Nov. 1). I haven't gotten my period yet, but I'm really concerned that it's not from stopping the BC but because of the possibility I could be pregnant. I took a pregnancy test last week and it was negative, so I took another one this Monday (11/ 7) and it was still negative.
Is there a possibility that I could be pregnant? I'm a college student and am really not prepared for this, and I'm not sure where to go from here.

Stopping your birth control can mess up your periods,it can take some time to settle into the natural cycle again.
You are 1week late, if you go by your previous cycle-your period was due on the 1st,so it is still early days.
I think it is possible to be pregnant,but I would be surprised,more likely due to you stopping your BC to soon in the month.
I think you are going to have to give it more time,for you body to re-ajust,having stopped BC.
Should you still not have had your period within a few weeks( leave it as long as you can)visit your Doctor who may be able to tell you one way or another,however I suspect it's your cycle not right yet.

How late are you with your period? If it's longer than two weeks you're probably pregnant, two weeks isn't long enough to take a pregnancy test. I was showed negative on the test for almost three weeks, I'm 20 weeks pregnant today. Girls go to college pregnant, one of my friends is... it's not the end of the world.