Am I douching wrong?

OK, so I know there’s probably 1 million posts on here asking about this but I need some advice. For reference, I live in a dorm so I can’t use a shower attachment. Recently, I’ve just been using a water bottle which I know doesn’t sound ideal, but honestly it works quite well most of the time, but for other times such as yesterday, I went through cycles for at least an hour and by the end the water ran clear initially, but was still dirty at the very end. I don’t know if this is something I’m doing personally wrong or what but I have to think something is going on for it to have to take that long and still not be OK. I know I’ve seen people mention diet so I might try that, but I’m wondering if that can really make such a big difference or if another part of my process is wrong. I could provide more details if it’s needed, but any advice would be appreciated!