it had occured to me more than once that while urinating(before deficating so i am seated) that a sticky fluid will come out of my penis. i am not sure it's semen but recently, i think it has stop. do i have some kind of disease or cancer or something?

No not at all. This is something that may happen from time to time, it has happened to me several times in the past. Usually it is more likely to happen when there has been a longer period of time between ejaculations but that isn't always the case. The same muscles you use to urinate or deficate are used in the process of ejaculation. So, from time to time they will allow the release of some semen as well. However, the opposite is not true, when ejaculating you will never have urine included, our body is designed so that isn't possible.