You cant get through exam by chanting mantras all the day.You have to chant mantra only for 20 or 30minutes.
You said that you have no birth data.No problem.
It is clear from your mail that you are suffering with a mental obsession and also having a marriage problem.
Stop all medicines,if you are taking any medicines from the psychiatrist.
You have to do penance for one year to get over your mental anxiety(depression) problem and marriage problem.
You have to do penance(tapas) for one year by avoidinng milk products(milk,curd,buttermilk,
coffee,tea),sweets,nonveg,fish,eggs,nuts.You can take other foods and tiffins.
YOu have to daily take two headbaths with cold water,morning and evening.
You have to chant mantra daily for 20 mins only..
Easy remedies like japa,puja or homam will not work..Body suffering remedy
means tapas method remedy.
You have to do fasting once in a day,for one year.On the day of fasting,you can eat
uncooked vegetables(unlimited quantity).. firstname.lastname@example.org