Plan B is a pill you take
after having unprotected
sex, it is supposed to stop you from ovulating for a few days so the sperm can't meet an egg, it is not an abortion pill so it is not 100% effective. Plan B is not a form of birth control, if that is what you are looking for you need to go get some from your doctor.
To answer your question, yes, you could be pregnant.
You need to educate yourself on the matter if you are going to continue having sex.