I have been on birth control for 3 months but it has not been perfect use the last few weeks. I finished my period 2 days ago but did not start my birth control on time. I took my first pill tonight but I had unprotected sex with my boyfriend who usually pulls out but didn't this time. Is plan B necessary? I have heard they are very bad for you, mess up your cycle and have nasty side effects. I don't particularly want to take one.