Ive been on bcs for a month when i have unpretecd can i take plain B or will that mess up the bith control?

so ive been on birth control for a month and my boy friend and i really dont wanna use a condom and im just worried that i might get preg now i wont see him for two or three weeks from now and im taking the birth control everyday but just in case after we have i wanna know if i can take the plain b pill and as well continue taking my birth control helppp me