You either have an injury from the act itself or you have hemmorids from the symptoms you mention.
Yeah, I agree. What is the product that is giving you relief? Have you considered going to the doctor?
I really think you should go to the doctor since you mention unbearable pain. Pain is the way our bodies tell us something is not right. I know no one wants to go to the doc because of anal issues, but you will be far from the first one your doc sees for that reason, or for symptoms after anal sex.
Was it protected anal sex?