What Causes Bleeding After Masturbation?

I am 16, 5'7.5, weigh 140 pounds and don't have a medical history really. I was masturbating today and after I ejaculated, I tried to squeeze out the last bit of sperm from my penis using my hand starting at the bottom and pulling to the top. Then a little bit of blood got on my hand. I usually always do this after I ejaculate and this doesn't happen. I remember that once it happened a couple years ago and I remember when it did I had started to masturbate more often. Also this time, I increased my amount of masturbation in the past week and yesterday my penis felt soar but I still did it again today and this happened. I don't know what's going on and am to embarrassed to tell my parents or meet with my doctor about this. I have no other symtoms...Can you tell me what's going on?