Hello Mr Junaid,
is quite common even among married men. There is nothing wrong with it and you should not harbour any guilt or negative feeling about that.
So fantasize and enzoy as you are... since 8-9 yrs.
Rest assured it does not cause impotency or infertility
and it is not going to affect your married life.
If needed you may consult a sexologist
I hope this answers your query, I will be glad to reply any follow up query that you have.
Wishing you best of health.