Second time having sex we used a condom but there was white stuff when he pulled out were unsure if it's sperm shall i take my sisters corrective pill?

Not sure I entirely: understand. If the condom didn't break and was applied properly, it has a very good chance of preventing pregnancy. Hard to know what "white stuff" may be ... ? talc to aid in condom placement? The Plan B pill is only for emergencies; this doesn't sound like one. But if greatest pregnancy prevention desired, strongly consider female hormonal contraception: implant, IUD, pill. Stay well:)