First off find out howmuch it really bothers you?? like do u wonder have they ever slept together get him to answer all those question but dont make it into an argument! just tell him how u feel!
I for one wouldnt have a problem WITH IT my boyfriends best female friend is a stripper and to be honest she really cool and fun shes never even made me feel insecure about nada same with him so i mean i got no problem with it plus they have been thru a lot together but nope.
You should talk to him and if he truly is in love iwth u he has eyes for nobody else trust me!