When I touch my scrotum, it feels like one testicle is smaller than the other and is also a bit thinner. I am not feeling any pain. The thinner testicle is lose and falls a few times! I'm 14 years old and had been masturbating, but I've stopped now. Is this difference in size of testis a concern?
A small variation in testicle size is normal in men, especially during the years you are growing. A noticable difference could indicate that one isn't developing properly. This could be due to a wide variety of reasons, such as a undescended testicle in early childhood or mumps. You may want to ask your doctor, but there isn't likely anything that can be done about it at this point.
If it is a poorly developed testicle, it won't affect your manliness in any way. Your other testicle will make up for its lack in producing hormones. You also will still be able to father children, though it might take longer to get your wife pregnant since you may not have as many active sperm in your semen. There are ways to enhance the odds if this becomes an issue, but we can talk about that later as marriage is still a ways off for you.