Hello please I want to know while my dick fall...

How to treat loss of erection during sex

you can use drugs like sildenafil or vardenafil to strengthen the erection and you should avoid stress and this problem may be caused by diseses like multiple sclerosis which is treated by beta interferon and it my be caused by Parkinson disease which is treated by carbidopa  and the causes  may be depression which is treated by antidepressant under supervision of the psychiatrist

how to diagnose  loss of erection during sex

when multiple sclerosis is suspected then MRI should be done on the brain and the spinal cord and to exclude Parkinson disease then dopamine transporter scan can be done

what is the causes of loss of erection during sex

fatigue
stress
multiple sclerosis
Parkinsons disease

what is the symptoms associated  loss of erection during sex

in  multiple sclerosis there will be numbiness and weakness in different body parts
in Parkinsons disease there will be tremors 
generalised fatigue

advise

you should follow up with andrologist to provide the treatment and to assess the case