Sometimes in a while, (once in 2 weeks or month) i notice that while bowel moment during stool, rice like small substances come out of my penis. they're similar to lumps in my semen sometimes. i don't masturbate regualrly, get wet dreams once in a w?

This is normal from time to time in some men. Pressure from straining plus stool passing through the rectum is squeezing out semen from your seminal vesicles (where semen is stored for the next ejaculation) or prostate gland fluid. With no other symptoms (like painful urination, penile discharge at other times), probably nothing is wrong. Get care if other symptoms or it becomes more frequent.