I am 26 year old male. I will get married soon. But I have one doubt. Some day before I had sex with one women she was jus 8 years bigger than me. During sex I feel I am not sexually strong because first 15 minutes there is no any tension in my penis. I tried all way to stand my penis but its not get stand. finally I did but its not that much satisfactory. During watching sex video my penis get enough stand and during hand job also it get stand but why during sex there is no any stand in my penis. I am so varied about it please help me or suggest any medical treatment. I want to leave happy married life.