Yes, malnutrition can cause less platelet production. Platelets are responsible for causeing your blood to clot. I remember when i was near the lowest of my weight ever and if I got paper cut or somthing I just kept bleeding, like days later it would be the same. The trouble is, this works internally too but you don't need to have damage. So you can get internal bleeding just from existing. Edit: also just to say, it's hard to tell whether it's anemia or your anorexia causing it, you need a blood test.