I've Been Having Unprotected Sex With My Boyfriend And Usually

I've been having unprotected sex with my boyfriend and usually I take a Plan B pill the next day if I feel like there's a chance he got sperm inside me. I took one less than 24 hours ago after having sex less than 72 hours prior and after having sex again and knowing there's a chance he got sperm inside me, I need to know if it would be bad to take it again? If I can, how long should I wait? This will be the fourth pill I take, is that too much?