See dear..simple way to avoid pregnency is to avoid sperms to enter ur gf's vagina..but as u said u both are virgin and still wants to remain virgin there is no chance to get pregnent coz virginity breaks only if u do intercourse..in foreplay u can enjoy as much as u want..and it also plays important role in sex...u can suck her vagina..let her suck ur penis,lips to lips kissing,huging,fondlind,licking,pampering,etc can be dont without hesitation in foreplay..it also involves fingering ur gf's vagina..just to excite her..
Still if ur doubt isnt clear..write ur comment..and also send ur feedback..thank you