Don't buy the bad stuff!!!! I know that sounds easy but if it's not there it will make it easier for you not to eat it.
I would second the comment about drinking enough. You are more than likely thirsty rather than hungry. If you are gaining weight then you don't need all the calories you are taking in to sustain breastfeeding.
Have a great big breakfast. Porridge, followed by fruit and yogurt or wholemeal toast. Boiled eggs and soldiers, omlette etc - something that will really start you off well for the day.
Every time you sit down for a feed have a pint of squash (no added sugar) next to you, a banana and a yogurt, or a fun size chocolate bar, or a cereal bar etc etc. It will take a while to break the habit of cake and biscuits during a feed but this will REALLY help! It's the habit of eating something that you have got into so you need to make sure it is a better choice.
Try making your meals more healthy as well - curry and pie are high in fat and not neccesarily normal "healthy" meals.
Try more pasta based meals with low fat tomato based sauces that will fill you up for longer - roasted veggies and tinned tomatoes, grilled meat or fish with baked potatoes and loads of veggies. Jacket and beans or Beans on toast/eggs on toast for lunch will fill you up. The key is to fill you up with less calories.
Homemade soups are a great one to fill you up and you don't need to spend hours cooking - cook up a huge batch at once that will give you 4-6 portions and then freeze them. You can also freeze the soup in small mug sized portions and blitz in the microwave and have a cup of soup during a feed.
Puddings - a whole tin of semolina will be giving you 335 calories which is quite a lot!!
Try and have yogurts and fruit for pudding - maybe save the naughtier stuff for the weekends.
Swap high fat spreads for lower fat ones and eat wholemeal bread instead of white. These changes will really help I promise!
I know it's tough when you feel hungry all the time but it doesn't have to be "bad" food. Lots of water and fruit and veg will be great for your skin and make sure that your milk is great quality as well!
Go for it - you can do it!