2006 Nissan Wingroad Engine Vibration / Excessive Oil Use

Hi,

For about a month I have had to keep topping the oil about once a week as it seems to be going through a lot, I have checked for leaks but can not find any. I recently had to get the Crank Shaft Speed Sensor replaced as the throttle was going crazy, at the same time it was lacking power as well, after getting the speed sensor fixed I assumed that was the issue with everything, but the power is starting to lack again and now the engine is starting to shake violently if I accelerate, sometimes it will have smoother patches depending on what speed I am going but it still seems to be in a very serious state.

Have booked it in with a mechanic but that is a two week wait and they didn't offer any advice in the mean time.

Any thoughts on what this could be and how serious it is?