Saying Shahadah would be necessary in the case that want to choose your religion as Islam. (Of course you say Shahada in your Salahs everyday)(اَشْهَدُ اَنْ لااِلهَ اِلاّ اللهُ وَحْدَهُ لاشَريكَ لَهُ وَ اَشْهَدُ اَنَّ مُحَمّداً عَبْدُهُ وَ رَسولُهُ).
But if you really did a Kufr as an practice which made you as a Kafir, then you ought to say Shahadah as well.