how can i fix my internet connection?

i have Bulldog broadband connection,to connect i used to click the Speedtouch icon,now when i do that the 'usb diagnostics' screen appears instead of the connection one with my username & password.I now have to go to Start,Connect To,then Speedtouch appears in the Dial Up part,it connects.Now my internet connection is extremely slow and i have no idea what to do! Also i have problems opening attachments from emails i receive.What has happened?? Can anyone help!!