Thanks for using DoctorSpring.com for posting your query.
I have gone through your question in detail and I can understand what you are going through.
The condition that you are suffering is called premature ejaculation. Now it's a type of anxiety disorder and the person normally suffers from performance anxiety where in he is anxious if he can perform or not.
First you can try the start-stop technique. Your partner is supposed to start stimulating you and the moment you are about to ejaculated she is supposed to stop all the stimulation and hold your penis head hard. Now this should be repeated.
Perineal exercises also help. These are the muscle exercises that occur when you contract the perineal muscles like when you are trying to stop the urine or feces. You have to do these contractions repeatedly daily to tone up the perineal muscles.
One solution is medications. Some patients are not willing to wait for these acts to produce results and instead demand medicines. I prescribe them 12.5 mg paroxetine at night and they are doing good. Normally one should try until 25mg of Paroxetine. If paroxetine is not effective then Dapoxetine is an option. It has to be given 1 hour before having sex and will prolong the sexual interval.
Hope this helps
Dr. Srikanth Reddy MD