Bleeding after masterbation...AND I'M PREGNANT!

I had a little scare the other day when I masterbated. After I was done and to be blunt (I didn't insert anything into my Vagina) I had a pretty mild cramp for about 10 seconds. I'm also about 4-5 weeks pregnant. I went into the bathroom and when I wiped, there was a redish-pink tinge that wasn't high in content. It lessened after a few wipes, and now I don't have anything wrong. I read about misscarriages and I don't want to lose my child. This is my first pregnancy and I don't have a doctors app't. until a week and a half from now. Does anyone have a clue as to what might have happend? Should I be worried and go to the hospital? Please help soon, I'm scared out of my mind and only 18 years old.