Exactly a week ago my boyfriend and I were having sex and his semen splashed back and we think some of it might have gotten inside me because it was all over the outside of the condom. To be safe I bought a plan b emergency contraceptive and today I noticed light bleeding throughout the day. Is it possible the plan b induced my period? Or is that just a side effect of the plan b? (I will be switching to a more reliable birth control method soon like the shot or the pill)