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The time of 10mins is fine as the normal time is around 3 mins so you are normal.Whether you take over the counter medicines or get prescribed viagra
the time may increase but please understand 3 things:-
-you are not going to take those medicines life long so even when you stop it you will miss them and feel that your time has reduced and so you will feel as you have grown weak.
-if you do sex with your girlfriend with help of medicines to increase the time then your girlfriend will never be satisfied without the medicine
-Even if you do sex for hours you will get pleasure and satisfaction only when you get orgasm that is when the sperms are discharged and remember that pleasure is only for few seconds .
So please try to stay away from these medicines and enjoy natural sex and you will be happy.
I hope my answer is helpful to you .