Did the Muslim commit a sin out of heedlessness when he intended not to perform ghusl for the sin of obsessive whispers, then reevaluated himself and felt guilty, and is he considered an infidel if he judged himself to be an infidel?

Dismiss these obsessive thoughts and strive to repel them. You are engaged in a great good, and you will be rewarded for this struggle. Your aversion to these obsessive thoughts is proof of the sincerity of your faith. You have not left the fold of Islam due to these obsessive thoughts, nor are you required to perform ghusl or renew your Islam. Reject these obsessive thoughts and continue the struggle. You may consult trusted doctors or the consultations section of the website.