Facebook iPHONE app appears to compromise my account. HELP!?

[Hey help]

It blocks my account and says: "Sorry, your account is temporarily unavailable, please log in to facebook.com from your computer and follow the instructions given"

Then I go t my computer and try logging in and it says: "Your account was recently accessed from a location we're not familiar with. Please review the activity details below" and under that it shows a map pin-pointing Wellsboro Pennsylvania, US. I'm not from Wellsbroro or know anyone there.

This is over and over again whenever I try to log in with the Facrbook app on my Iphone. I've changed my passwords so many times already.

What could it be? Is the app given by facebook on mobile to browse faster safer or a scam? Does it happen to anyone else? Is it safe? O.O?