Pradeep,
Please don't lose hope. You find Threads difficult probably because you have been avoiding it most of the time in your career. Some of my friends during college also have faced this kind of problems. My suggestion is, don't be scared of any subject under Core
Java, because Java was intended to be simple. Outside Core Java it's Ok, if you are scared of certain things (I'm scared of a commonly used XML parser API)

. Mere reading through SCJP books (no matter how many times) may not do much help; you need to assimilate the ideas and concepts expressed in the books. When you understand and begin to appreciate what the book is talking about, you will not have to put any extra effort to memorize most things. K&B is an excellent book but it is not for reading in haste. Work diligently and clear the exam. I wish you Good Luck.
Regards,
Sujan