Thanks for your query,based on the facts that you have posted it appears that you have problem of leakage of semen while passing urine .
Please note that what you suspect it to be semen is not a semen but excessive secretion of mucus glands located in Bulbar Urethra.
You ejaculate when having a foreplay with your wife,This is due to excessive sexual stimulation and anxiety resulting into ejaculation before you get engaged in sexual intercourse.
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
3)Take anti oxidants like Almonds 5-6 everyday..
4) Avoid alcohol and smoking..
Please consult qualified Sexologist