Itunes passwords

[pidget]

Will try and word this so it's understandable, had to change my password for itunes last week and thought no more of it until I tried to put an app on my iphone yesterday-put in my new password and it didn't recognise it so had to go through the whole registering/password thing again. It let me put a game on the phone using new password but when I tried to update apps just kept saying 'cannot connect to itunes store', thought I would try through laptop and it says there are 6 apps to update but when I click on it says no updates available??!! All too confusing for a technophobe like me-please help, if only to save my phone going through the window!!