This is not abnormal as a human being. You need to now decide whether you want to spend rest of your life thinking of the past whether pleasant or unpleasant;  or do you want to move ahead in life which is really much beautiful than you think.  You are just 25 years old and long way to go. It seems that you have given the key or happiness to your so called ex and probably he must be having nice life. Decision is your hands dear young lady