don't ever say "i swear", it just messes it up, put a truthful look in your eyes and don't smile unless it is funny (Not usually) this has happened to me 3 times do things like say "I am not lying i promise, please believe me" and put sad and truthful words and add look in your eyes
It is very difficult to prove to someone that you are not lying. To prove that you aren't lying without the backup of hard evidence can be so difficult. However, if you have a friend of yours who he trusts, you can ask her to be your ally when trying to show your boyfriend that you are not lying.
my friend asks me this every single day. and really what are you doing for him to not believe you? if nothing then he has low self esteem. sometimes it doesn't matter what you say, you can say it over and over again, and he wont believe you. my friend doesn't talk to any boys at all and he still doesn't believe her. i ask all the time why are you still with him and she says 'because i love him'. gain control of the relationship, because if he cares that much about boys talking to you then he obviously wont let you go, when you pull him up for it. i think you need to say i can talk to ever i want. i love you but without trust there's no relationship..