This can be the symptom of the Plan B
mainly. As you told that you already started taking birth control pills and after 4 days you have unprotected sex and that too without ejaculating inside you and you also taken the Plan B within 3rd day. So the chances of pregnacy after all this is very rare.
This problem can be because of the over dosing
of the hormones which you have taken in the form of your regular birth control pills and the Plan B. Since both birth control pills and Plan B has hormnonal component in them and important difference between them is the dose which is very high in case of emergency contraceptive
pills like Plan B. So becuase of increased dosing, these types of problem which you are facing can be there and they are also common side effects for using Plan B types of drugs.
Thanks and take care.