Ok, I'm sorta worried for you on all counts.
If you're consistently eating junk food, and large amounts of it, then you need to be worrying about your general health. All the food you described is a lot in terms of calories. The average slimfat muffin has between 300 and 500 calories in a single one. Scary!
Anyhow, my shock aside (sorry about that), I think that the start of the problem is the calorie limit that you're working with. Sure, in the short run you might lose some fat, but your metabolism might well drop, which will bring an end to any fat loss. I think of 1200 calories as the absolute minimum anyone of your size should be taking in, even without exercise, and I'm curious to know how your trainer came up with that figure.
I'm not an expert in the least so I'll say what's worked for me. More meals/ healthy snacks during the day, thus upping my calories so my metabolism remains high, and so I have enough energy for my gym workouts and STILL lose weight. You need to focus more on what you're actually eating - it needs to be good complex carbs, good fats (from oily fish, nuts and olive oil, etc), and protein.
The up side to eating a more balanced diet is a reduction of junk food cravings. I still occasionally crave junk food, but it's significantly less than before.
Of course these are my suggestions, and I'm not an expert. But I do think you need to look more into your food intake, as it might explain why there's so much junk food in your diet.
Good luck with it all