Dear sir, To start with, I must say there you are harbouring many misinformations because of which you are suffering from unnecessary anxiety. Unfortunately this is common in India where sex is a very big taboo still. Night fall in itself is not a problem. It is a natural phenomenon. So there is no question of weakness or any other problems because of it. What you are probably having is an anxiety syndrome similar to what syndrome. First of all visit a sexologist to understand anatomy and physiology of Sexual system. Secondly, you will need an assessment for inadequate weight if that is the case at all. Please understand a problem can be treated only if it exists. Have an authentic information about Sexual health. Then you can decide if there is a problem or not.

Hello. You need to practice kegel's exercise daily. Also, you can use Ashwagandha rasayana or lehya 1tsp twice daily followed by hot milk 1hr before food. Tab makardhwaj 1 tab twice daily. Use for 3 months regularly. You'll recover. Medicines available at Ayurveda stores.