Getting someone else's notifications on my iphone?

[greatboy825]

So, a few months ago (before I had an iphone) I frequently used my boyfriends iphone to instagram pictures. Later we broke up and I purchased my own iphone. However, now I get notifications from his facebook friends saying "your facebook friend 'john doe' had joined instagram". How do I make it stop?
**mega palm to my own face*** ___you are an idiot for writing like this____ I am no logged into his facebook. I have never logged into his facebook from my phone either. When I post pictures from my instagram account it goes to MY facebook and MY twitter. But I get notifications from his facebook, which is weird.
not logged*

[sabrina]

--mega face palm--- log out of his Facebook. Freaking idiot. -.-