I am 27 and I don't know how to explain it, but I feel I am not lasts in bed as a general healthy man does. I don't have any bad habit like smoke etc., my body weight is 55 KG which is not good according to my height 5'10". I have good stamina in my daily routine life or if we talk about exercise, but I am unable to satisfy my partner. I also have nightfall some time, but not very often.