What should I do about my feelings of anxiety, indecision, and inability to make a decision regarding marriage after performing Istikharah?

Scholars have differed regarding what the one performing Istikhara (prayer for guidance) should rely upon afterward: whether it is the expansion of the chest (a feeling of ease), the facilitation of the matter, or if they should proceed with it and only abandon it if Allah diverts them from it. The most authoritative opinion is that the one performing Istikhara should proceed with the matter after Istikhara and only abandon it if Allah diverts them from it. This is because the Hadith does not state that Allah will create in the heart of the one performing Istikhara an expansion towards one side, or that they will see a dream, or hear a voice, or have something cast into their mind. Indeed, the one performing Istikhara might not feel any expansion in their heart even after repeating Istikhara, and this strengthens the view that the matter is not dependent on expansion. So, if you find the girl righteous, proceed with her marriage and rely on Allah.