Boyfriend is blocking other guys

me & my boyfriend have been together for 9 months. we have each other's passwords to snapchat and stuff and trust has never been an issue. slowly he has been blocking some guys on my snapchat. first it was a few ex boyfriends(which i'm okay with because i understand why he wouldn't want them on my snapchat). then he began blocking boys that i never talk to. i never said anything because i never talked to them so it didn't really bother me any. yesterday, he blocked one of my closer male friends. obviously this is when things became an issue. me and this boy have been friends for about two years now and have never had anything romantic going on. him and my other three female friends all hang out often. the only time i actually talk to him on snapchat is in a group chat with him & my other three friends. this turned into a huge argument. the argument ended at the time being but i still have an issue that he is blocking any males at all, it makes it seem like he doesn't trust me. what can i do to approach the topic?