Thanks for your query,based on the facts that you have posted it appears that you have been indulged in masturbation
since many and now worried about sexual problems in future .
First of all there is myth in a mind of common man that excessive masturbation is the reason of all sexual problems But I would like to state that it has been discussed in scientific forums all over the world and proved scientifically that masturbation does not have any negative effect on any organ or system in the body.All the problems that you are facing now are mind related and due to anxiety
Following measure will help you to boost up your confidence and improve your general health .
1) Practice regular exercise for 45 minutes followed by meditation
for 1/2 an hour in the morning.
2) Take high protein diet rich in vegetables and fruits and Vitamin A
3)Take anti oxidants like Almonds 5-6 everyday..
4) Avoid alcohol and smoking
Masturbating twice a week is natural and nothing to be worried about.