What should I do about my feeling of involuntarily passing gas during prayer, which compels me to repeat it multiple times, knowing that this occurs due to anxiety and obsessive thoughts?

This feeling is a whisper (waswasa) and an illusion from Satan. Do not pay attention to it, and do not repeat your prayer because of it. Try to pray normally without caring about these thoughts, and do not repeat your prayer unless you have absolute certainty that something has exited. The cure for whispers is to ignore them and not pay attention to them.