Learn to perform cunnillingus dude. You can't just jump in all excited and start banging the shit out of these chicks. It sounds like they're not warmed up for it so they're chaffing which hurts, which stops them from lubricating at all, which makes matters worse, and eventually you just scrape off a layer of their vagina which reaaly hurts if you can imagine. You need to do a lot more foreplay and slow the fuck down.