Do not let the waswasa dominate you. As per the preferred saying the water becomes used as soon as it leaves the body. And as per the preferable saying used water is pure. Hence if the used water smears body or clothes then you should not be worried about it. Yes, you should perform wudhu in a way that the splashes of used water do not fall upon you.
Allah knows Best!
Darul Uloom Deoband