how many head bangs are too much

last Tuesday my daughter hurt her head on the dinner hall floor in play group and she bruised straight away, Saturday gone her and my partner fell down the stairs she bruised her face by falling onto the banister spindles and winded herself, and today she's lost her balance in nursery and hit her head on a radiator cover and marked her face....how do I know if head trauma is too much, I can't bear to see my baby girl hurt let alone have marks on her :( I feel helpless and I feel like I'm gonna loose her if she carries on hurting herself