If it's iMessage then he has your iCloud password, if it's carrier SMS then you are just over reacting, if it's email you are sending and he's receiving a copy of each conversation, then he has your email account password. If he can see your word documents photo library based on your iCloud, then he has your cloud storage password.
If you have a MacBook and use both your MacBook and iPhone for iMessage, iCloud Gmail etc... , then change your MacBook password too because if he have access to your mac, he have access to all your password ever entered on that MacBook.
If he's a tech savvy like me, you are out of lock. Change a boyfriend if he can't respect your privacy.
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