Need advice ASAP! -first time and very concerned

Angela
I had sex for the very first time with bf on Saturday night (it is now Monday). He thought the condom had broke but then said it was actually fine and continued; I'm not sure if I trust that. He pulled out and I am on MonoNessa birth control but my discharge turned creamy white and I've had really bad headaches.
I'm paranoid that I might be pregnant. Should I take a Plan B pill even though a guy working at Planned Parenthood said it wasn't necessary?
If I am to take the Plan B pill I would need to take it before 7pm tomorrow night so please any opinions are welcome!