Rocking him to sleep is killing my legs, im not just complaining for fun either i tried to kneel to…

Rocking him to sleep is killing my legs, im not just complaining for fun either i tried to kneel to put him in his bassinet and my knee got a sharp cramp and it buckled and I fell to the side and smacked his head on the wall :( im sorry baby hope hes ok, he woke up crying obviously but I dont see a bumo on his head or anything which is good. but my leg is killing me now it hurts to walk so much im not even gonna try the stairs :/