Hello
Thanks for using DoctorSpring.com for posting your query.
I have gone through your question in detail and I can understand what you are going through.
Your concepts are true. Its right that its only the outer third of vagina that is sensitive. Rest of the vagina is expandable and is not sensitive and even if the penis is anywhere bigger than 4 inch, it wont matter. Your size of 4 inch is perfectly normal and you need not worry. You can leave this embarssment and enjoy the sexual act.
Hope this helps,
In case if you have any further query, do let me know.
Kind regards
Dr. Srikanth Reddy

Hello,
You need to get it examined by a surgeon to rule out phimosis.
Ideally the skin should open up completely exposing the glans during intercourse.
You may face problems, if that is the case.
Also, no, there will be no problems in procreation.
Regards.

Hello,
There are no such medicines, and all the internet advertisements are mainly only for publicity purpose.
The normal duration is 7-10 minutes.
Regards.

Hello,
Yes, any condom will fit your penis.
Please do not worry,
I will tell you something from my own experience dealing with patients. The more you seem to worry about this issue, the more issues you face with erection and sex. Please be strong mentally, and rather focus on enjoying sex. Your partner will understand not everyone has very big sized penis in India.
Regards.