@madasa666 the 2.5mg dose is not clinically proven for sustained weight loss, it is a starting dose to get your body used to the medication without too many side effects before increasing to the clinical starting dose of 5mg - and upwards.
It does appear that our individual sensitivity to MJ varies massively, either in terms of side effects, the level of suppression, or the rate of weight loss. If you look back at older threads you will find several posters who were the same as you on 2.5mg but really got into their stride as the doses increased. Hopefully that is what you will find too. It can be hard to read posts at times because often people are more inclined to post enthusiastically when their weight has dropped, so we might see more of those posts than others (although not on this thread at the moment!)
Once you feel good supression you should find your desire to eat rubbish decreases. Once you get to that place it can become even more important to plan your healthy food and prepare as much as you can, as your appetite for food buying or menu planning may become less too. And the process of breaking down fat needs water (for the biochemical reaction) so you should also plan to drink lots of water/herbal teas/electrolyte drinks etc.
Is the 'rubbish' biscuits, cakes, crisps etc? Irrespective of your weight none of that will be helping you. Are you buying it on impulse when you're hungry or do you have it readily available in the house? Is there anything you can do to help with those habits? On a previous (non-medicated) diet I kept peperami sticks in the car and would eat one, maybe even 2, on my way home from work. Not the healthiest snack but it took the edge off my hunger and prevented my from stopping to get petrol (or whatever excuse) and buying sweets and crisps to munch mindlessly.
Good luck on 5mg, and onwards.