Hi,
If you think that it's definitely urine, don't drink anything up to an hour before you have sex, and try to empty your bladder completely just prior to sex. Also, practice kegel exercises to strengthen your pelvic floor. You may also want to speak with a gynecologist about this if it continues to bother you; the doctor could probably advise you best.
Good Luck
I believe you must have talked to some Professional one.You may find squirter's group and match you notes.I think I read somewhere that urge for peeing is orgasm and on should let go(release as orgasm). Yes there would be mess. So we have to prepare ourselves with towel and cleaning clothing.You may google for squirters. (sp?)