Holding in poo is bad for you??

I'm a 16 year old male who has been holding my poop in ever since about the age of 5. I hold it in only for about 10-15 minutes daily. I recently stopped this bad habbit out of fear of dangerous bodily harm. But I can't help but wonder, is it too late? Could harmful damage such as cancer already been done? I've heard you can get prostate cancer from this. Which to me makes sense because sometimes after I hold it in then masturbate, my urine tract is all messed up and feels like I have to keep going. Well anyways, do you think I'm safe now or have a high risk of something based on the past?