I'm on low caloric diet for 3 months now first week lost about 8 pounds then now i'm losing 1 pound a month is that bad, and means diet failure ?

Not at all.: It means it is working . You need to be patient and persistent to have good result . Even if you do not lose weight , that should not discourage you. You may have to add regular exercise to it though to get better result

Not optimal: The early weight loss may have been fluid (water) weight. Subsequent 1 lb per month is suboptimal. It may be that your caloric restriction has caused your body to reduce metabolism. Would evaluate number of calories in, as well as exercise pattern. If your calorie intake is very restricted, it may be that you need to increase calories some and increase exercise to meet your goals. Good luck!

Low fat diet: Congratulations for sticking to the diet for so long. It is very common to hit a road block . Most common reason is slowing of metabolism. Not eating breakfast, not exercising, constipation, not sleeping well and increased stress.