Thank you for your message. I am sorry you are having this problem.
Let's start with "no". The model does not understand the concept of a word being negated by the word in front of it. So using "not [X]", "no [X]", and "without [X]" does not work. As you observed, it ignores the negation word and add to the image the thing you are trying to avoid. You basically need to find "positive" words and phrases telling the model what you want to see rather than telling it what you do not want to see. Such as "flat land" rather than "no mountains". If I am not sure how to describe something I want to exclude in a positive way, I will ask Google Gemini or ChatGPT for ideas. Just be aware that when they give prompts, they are usually too wordy and conversational, so you have to edit them, but they are good for ideas.
"White background" should generally work. Can you please share your prompt and the results? Possibly something else in the prompt is leading it in the wrong direction.