Over 40 and trying to conceive

Just wondering if anyone out there is having the same thoughts as myself - I think my hubby is stopping the sperm being realised when he gets the urge. He doesn’t this funny movement when I think he gets the urge for the swimmers to be realised! It’s really hard to explain - to stop all those horrible thoughts going around in my head - we have sex and every time it comes to releasing and getting the urge he does a movement which makes me think he is stopping the swimmers coming through - my question is can men stop the urge of the swimmers being released????