How do i log myself out of twitter on a different iphone?

[Nick]

There is no easy way to do this.

I would say you have two options, and don't necessarily guarantee complete success.

Both options require you to go to https://twitter.com/settings/account

1. Check the "Require a verification code when I sign-in", as your boyfriend is already signed in, I don't know if it will prompt him for this, but it's a possibility.

2. Probably your better option, would be down at the bottom "deactivate your account". This will NOT delete your account, all of your settings/data/etc., are stored for 30 days. So after deactivating your account, simply reactivate and hopefully this will cause your boyfriend to have to re login to your account (barring you changed your password, this should keep him out).

Good luck.