hi..thanks for writing...i have understood your concerns.. the penis size varies depending upon the race and geography..like negros have big size penis and chinese have smallest size...but size doesnt matter because the sensitive part of female vagina is lower one third, which is less then 2 inches.. if you have 4 inches of penis after erection then it is sufficient for adequate sexual pleasure..so you need not to worry.. whenever male gets excitement, his penis erects..the pre-ejaculatory fluid sometimes is discharged, which is a prostatic fluid and not a semen, it does not contain sperms..it is watery liquid type..does not smell like semen..semen actually comes only after achieving orgasm... premature ejaculation is different thing in which orgasm is achieved early within 1 to 2 minutes of starting sexual activity.. i hope i have answered your query..if still you have question feel free to ask...best luck..