Frames Issues

So I play league a lot, but recently my frames have been really bad. I don't know why but there always at 11 and 12 when they use to be 50 and 60 frames a second. Please make recomendations on how to help or if this is a bug, riot please fix this. This is the same computer and the only device with wifi in the house is my computer i don't see why this is happening.