I would suggest starting a food diary, recording everything you eat and drink each day and noting down the carbohydrate content of everything. You might find something like
Collins Gem - Carb Counter useful for fresh ingredients where you don't have a packet or to refer to. Just stick to your normal diet and see what it reveals. This can help you identify areas where you might be able to substitute high carb items with lower carb alternatives, or perhaps reduce portion sizes and increase portions of lower carb items - e.g. less potatoes, more carrots and green veg. Lowering your overall carb intake will mean less insulin and hopefully a halt to the weight gain.