U can try masturbating 3-4 hours before sex. It will make you last longer in bed.if u r overthinking about ur ability to satisfy your partner, u need anxiolytic medicine before sex to overcome this. There are also medicines available in market to increase lasting time 4-5 times. U can consult me if further queries. Semen production goes on in the testis for 24 hours and gets stored in seminal vesicles. Now imagine seminal vesicles as a water tank. 24 hours production at some time, will make tank full. Its storage capacity runs out. Now overflowing mechanisms take place like night falls and seminal discharge in urine. To avoid this u need to have sex or masturbate regularly.