need advice!

I'm 5'5 and about 135 kg. I want to 120lbs. I have over 120 before, and I know I can do, but I am with such a time. I quit smoking and won last year, about 20 pounds. I managed to lose around 5-6 kilos, but now I'm stuck. At first, I was about 45 minutes. Then I got up the intesity interval training. Now I go for about 45 minutes in the morning for a steady 4 mph. I always watch what I eat. In the state of 1200 - 1500 calories, but I will say that I lose the recent time is my problem, I know. But what I need help finding what I did wrong exercise wise. I know I have to stay around 1200 calories to lose weight, but I think I am also adopted to nutrition and strength training in this way. Please help us would be great!