Its probably your scope. I had a scope on a .22 once and went shooting some tin cans or something and it was off, tried to sight it in and it was all over the place. A friend of mine told me that sometimes the crosshairs start to float on cheaper scopes (i think he called it float, its been a number of years). Got a new cheap scope (well its only a .22 no need for an expensive one) and everything was fine after that. (if it happens again, ill go get another cheap one too). You can use the messed up scope as a cheap spotting scope or a monocular.