Since past 1.5 years, you feel sad and you get suicidal thoughts along with crying spells, with nightmares about the same.
It seems that you are suffering from depression along with symptoms of anxiety. I can understand how difficult it must be for you to deal with these thoughts and feelings. Your thoughts about suicide are concerning and it is advisable that you consult a clinical psychologist as soon as you can to diagnose the problem and to begin the treatment.
Depression and anxiety even in its severe form are treatable with psychotherapy and medicines if need be.
Next Steps
Consult a clinical psychologist to get a detailed evaluation done to work on the problem from the root cause.