I have been having trouble with doubt in najasat and I over-think everything. My husband has been living here for so long and he is used to not washing (with water) after using the bathroom. Sometimes when he does not use water he scratches that area with his hand, which might be sweating. Then I think when he touches anything or me that it will become najis. Am I over-thinking this or should I ignore it and pray without overthinking about it.
Do not worry about your husband spreading najasah after he uses the bathroom. Even if he sweats, you are not sure that it creates enough wetness to transfer najasah. Furthermore, you are not sure that he actually touches the najis part specifically. And even if both those conditions exist, you do not know that he touches something else while his hand is still wet. It is highly improbable that all three of those things happen, and the smallest bit of doubt is enough to say that something is not najis.
If you continue to be obsessive about najasah, there is a chance you could harm your faith (God forbid) because practicing religion would become unbearably difficult for you. Islamic law does not intend to create hardship in the matter of najasah, and there is wisdom behind this. Follow the way of pious people, who do not obsess about najasah while still observing their duties. One should not allow his or her mind to be unnecessarily preoccupied with cleanliness, for it will prevent him or her from more important acts of piety, like controlling the tongue, focusing in prayer, etc.