Screeming baby?

My dauhter is 7 1/2 months old, and we have been having a huge screeming problem, she will sit/lay in one spot screming and whn somone goes to pick her up she gets louder and will hit them, she will roll on her tummy and stop cryin once in awile but hen rolls on her back and screms again, she isnt hungry or gy or even wet, I have tryed giveing her baby tylonal( she has been tething on and of since 3 months) she cant be bored because when she is bored she wants to be held and played with, the only thin I can think of is yesterday a friend of mine was watching my daughter and she invited another 4 kids over an on of the kids was pinching my daughter but that was over 24 hors ago and i dont think she would be sore today.(Not leaving my kid with her again ever) Whatd you think it could be?