Hello Thanks for query .Based on the fact that you are getting erection during foreplay but loose erection on attempting to have penetrative sex . This is mostly due to what is called as Performance anxiety.Following measure will help you to boost up your confidence and getting good erection and delay ejaculation. 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,C,D,E.and Zinc 3)Take anti oxidants like Almonds 5-6 everyday 4) Avoid alcohol and smoking.. Taking Sildenafil (Viagra)as on demand will help to get good hard sustainable erection and to have enjoyable sex. Dr.Patil.