Thank you for your question. There are two aspects to your question. The first is related to ejaculating quickly. You can learn to delay ejaculation by practicing when masturbating to hold on or use your pelvic floor muscles to manage your arousal. You may want to consult an andrologist or sex therapist to learn how to identify the point of no return and other technique to delay ejaculation. Sometimes hey may prescribe medication to help manage your arousal. Please read 'Managing premature ejaculation' by Metz and McCarthy. The second aspect is regarding your stamina. This can be improved by improving your general lifestyle including regular aerobic exercise, good nutrition, adequate sleep and managing work stress. As regards her pain, you will need to ensure she is highly aroused and lubricating well before proceeding to penetration. Most men who suffer with premature ejaculation rush into intercourse without waiting to see if their partner is ready. This makes sex dry and painful. You can use a lubricant to improve thongs if you wish. You can buy water based lubricant online or at your local pharmacy. hope this helps