Hi...This is not an uncommon situation.. Most men usaully ejaculate in about 3 to 10 minutes following penetrative sex, while it takes a longer time for a girl to reach her climax.. So it is completely normal if you are able to last for 10 minutes.. Increase the time of foreplay before begining the penetration, stroking and masturbation can help in making your girl friend reach her cliimax too...