What is the reason for imagining naked women and having blasphemous thoughts during prayer, and feeling constricted after ablution, despite sincere repentance, commitment to worship, and love for Allah and His Messenger?

What you are experiencing is a whisper from Satan, so strive against it and repel it from yourself. These whispers concerning belief do not harm you as long as you dislike them. Repel the thoughts and images that Satan conjures and do not indulge in them. Strive to guard your thoughts and busy yourself with what benefits you. Praise Allah for guidance and continue to steadfastly adhere to obedience.