I've been spotting. i'm on yasmin and took plan b twice last 2 week's. and negative pregnancy test. should i stop yasmin?

Taking plan B: along with Yasmin will likely cause the bleeding you see. If you have not missed any of the Yasmin pills, the plan B is not really helpful at reducing your pregnancy risk. Taking plan B will most always start bleeding when you stop the plan B. Don't stop Yasmin, take it regularly, don't use plan B with Yasmin. Use condoms to decrease infection risk.