Double placing or Double breaking

Hi,

Everything i try to place a block/break a block i do it twice(hit twice). This gets me very frustrated when I build cause everything's friked up.
I am pretty certain it is lag, Can anyone tell me a way i wont do this

Yes, certainly it is lag issues, do the most routine stuff, like cleaning up disk space, emptying the recycle bin, lowering your setting etc.

It is either your lag or your mouse.

This is caused usually by CPU taxing by other things rather than Minecraft. It occasionally happens when you've run Minecraft for a long period of time. It's not tied to framerate.