Hi, Thanks for writing in. Apprehension about the normal size of penis is a major concern for men. At 18 years age, you are too young to judge the size of your penis. It is made up of muscles and the growth at puberty and adolescent is under the influence of testosterone. A research study was done in healthy Indian males on penis size during flaccid and erect and the width of the penis. Mean flaccid length was found to be 8.21 cm, mean stretched length 10.88 cm and circumference 9.14 cm. Mean erected length was found to be 13.01 cm and erected circumference was 11.46 cm. If your penis measurements are at least as mentioned above then there is no need to worry. Semen flowing with urine is a misconception in most men at your age. If you feel it is present then it needs to be evaluated after clinical examination with the urologist. Any urine infection must also be ruled out.