Hi. Move forward in life as per your aim.

It can be due to some bad past history. You need counseling sessions to correct the same

Wellness Greetings to you Dreams are nothing but reflection of our subconscious thoughts.One may not be aware of this.  However we have been receiving thoughts associated with  fear and every other emotions ,that is happening in the conscious level .This has nothing to do with the memory .Sometimes even without your awareness , things which got your emotional attention goes Deep inside . aAll that have you mentioned could be easily evaluated as ,emotional.  This says that you are very sensitive and emotional things get inside your subconscious mind very easily.  Now the next step is we have to see why you are  extremely emotional these days or what can be done with all that. We have made them get inside ahead this is reversible too , this would be easy , if you can just talk to a professional and rewire this thoughts and program your mind to focus on the current situation which will be very helpful as you preparing for exams. Do not fear ,every thought of yours is as powerful as Any other Element. Focus on better and best things.  All the best for exams ,take care.