Is a woman sinful if she eats food that increases stomach gas, or if she doubts the emission of gas and tries to prevent it from escaping? And is she obligated to ignore urine splatter that she feels but does not see?

You have reached a significant level of whisperings (waswas), so do not give in to these whisperings regarding passing wind or the issue of impurity (najasa). Doubt holds no weight, for the Prophet, peace and blessings be upon him, said: "If any of you finds something in his stomach and is unsure whether something came out of him or not, he should not leave the mosque until he hears a sound or perceives a smell."

Nothing is judged impure unless you have certainty, such that you can swear an oath upon it. Frequent doubt concerning ablution (wudu) and prayer (salat) should be disregarded.

Abandon these whisperings and do not investigate anything that may have exited, no matter how much you doubt that something came out, until you achieve absolute certainty. For the religion of Allah is ease.

Do not pay attention to what Satan deludes you with. We advise you to supplicate, humble yourself, distract yourself from these whisperings, and consult a trustworthy psychiatrist.