Wow - this is puzzling. Since you say while 'ejaculating inside a vagina', I assume this problem doesn't occur from self-stimulation - is that the case? If so, I have no idea why sex would cause this but other activity would not. A couple of questions: 1) how old are you? 2) has this always happened when engaging in intercourse, or has it developed more recently? 3) was the sexual activity very vigorous? In any event, unless one of the readers/commentators on this site have experienced the same thing & found out why it was happening, I'm not sure anyone here can help. You might need to see a Specialist, probably a Urologist who specializes in treating men with various types of sexual disorders. Good luck - hope you find a solution for this - I'm sure it's quite troubling to the point you might even avoid sexual intercourse. That pain would probably take a lot out of the normal pleasure of intercourse...