What Causes Severe Pain And Bleeding During Bowel Movement In A Child?

I have a four year old daughter she has had problems pooing since she was a baby her poo was so big we had to pull it out a couple of times she crys about her stomach hurts it blows up like an ballon she bleeds sometimes we tired laxtives supportivers mirlax genelac changed her diet and all and still not working she don t like to poo she pee no problem only when she poo she tries to stop it she tries to hold it in just to get her to let it out I have to sit there and lean her forward rubber her back for about 30 mintues is there anyway you can help me find out whats going on with my little girl please I need some answer