Prince Nema, Apologies for the delayed response.
Based on my understanding of your issue description, where the custom domain isn't properly reflected in the URLs of newly created pages, and I see that you have tried multiple steps to isolate the issue:
In some cases, the URLs are stored in the database and need to be updated.
Check for any plugins that might be causing redirects or conflicts with the custom domain. (if you haven't done) - You may consider to disable such plugins temporarily can help identify the root cause.
1. Login to WordPress Admin
2. Click on Settings -> General
3.Find the WordPress Address (URL) and Site Address (URL) fields:
4.Update it to your new URL as shown:
5.Save Changes
Ref: WordPress: Redirecting to wrong URL
Kindly let us know how it goes. I'll follow-up with you.