Crosshair/ cursor inaccurate block placing

The crosshair/cursor isn't placing blocks as accurately as before. If your cross hair is too close to a line in the block your placing, the computer doesn't accurately register which side of the block in which you are trying to place another. If i can only see the bottom corner of a block and I got to place a block on the bottom, it'll place the block on the side. I don't have any odd blocks in my way either like fencing ect. im just seeing around another regular block and the accuracy is consistently poor