If you do something that you are unsure is kufr or shirk do you lose your religion, and could you provide evidence please? Are you sinful for it?
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُصَفَّى الْحِمْصِيُّ، حَدَّثَنَا الْوَلِيدُ بْنُ مُسْلِمٍ، حَدَّثَنَا الأَوْزَاعِيُّ، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، عَنِ النَّبِيِّ ـ صلى الله عليه وسلم ـ قَالَ " إِنَّ اللَّهَ وَضَعَ عَنْ أُمَّتِي الْخَطَأَ وَالنِّسْيَانَ وَمَا اسْتُكْرِهُوا عَلَيْهِ " .
Translation: Ibn 'Abbas said that the Prophet (ﷺ) said : "Allah has forgiven my nation [all Muslims] for mistakes and forgetfulness, and what they are forced to do."
Also, in the Quran, Sura AL-BAQARA (286):
Allah charges no soul except to its capacity. For it is what it has earned, and against it what it has gained. 'Our Lord, do not take us to account if we have forgotten, or made a mistake. Our Lord, do not burden us with a load as You have burdened those before us. Our Lord, do not over burden us with more than we can bear. And pardon us, and forgive us, and have mercy on us.[..]
If you mean by 'unsure' that you think it may be Kufr, you should either just leave it or ask a Shiekh, the Prophet (ﷺ) said:
That which is lawful is clear and that which is unlawful is clear, and between the two of them are doubtful matters about which many people do not know. Thus he who avoids doubtful matters clears himself in regard to his religion and his honor.