Is it normal that i dont cum with sex

well...here it goes

My GF is the only person who knows this...well her and the past 3 GFs anyway.

i cant orgasm with sex, i mean seriously i hear these stories of guys who put it in and cum, just once id like to do that...
solo i perform fine, 30min to an hour(sometimes more) and im done, but with sex, it just doesnt happen, and its not just once or twice...everytime, id like to see a therapist about this but i dont even know where to start asking.

actually i lied before when i said only blah blah knows etc etc i did say to one of my guy friends once...to see if he ever had the same problem, he thought i was just lying about how long i can last.

that is the other problem, my GF has tried to stay on it until i cum as we thought maybe she was too quick for me but all that happened was my genitals were aching as were hers (great sex tho)

and on top of all that, we have been thinking about children but if i cant perform dont wanna go down fert treatments

well think ive complained enough. please help :p