Maybe it's more a question of portion sizes, as Kellicopter suggested. Check your portion sizing here
. Another way to control portions is to divide your plate up. Fill half of your dinner place with veggies or salad, one quarter with starchy carbs and the remaining quarter with lean protein.
Another thing to consider is the type of carbs you are eating. Potatoes are quite high GI so they don't leave you feeling full for long. If you don't want to give up potatoes then consider switching to new potatoes which are lower in GI. Or you can allow the potatoes to cool after cooking. This lowers their GI, even if you re-heat them again. Pasta is quite low GI, and can be made lower in the same way as potatoes by cooling after cooking. Buckwheat, pearl barley, sweet potato and yam are all quite low GI. Add more protein to your recipes to further lower the overall GI. Wholegrains tend to be lower in GI because the protective husk slows digestion.
You can find a list of low GI foods here
You say that you try to exercise every day. If your exercise has dramatically decreased yet you are eating the same amount that could explain your weight gain. Also consider whether you've changed from high impact exercise to low impact exercise. If so you could be stimulating your appetite more because high impact exercise tends to suppress appetite for a while after exercise whereas low impact exercise like walking tends to make you hungrier. If you have dropped muscle building activity this could slow your metabolism so you might want to add some resistance work.
You also say you allow yourself a treat every few days. No problem with that, but are your treats slowly increasing without your realising? You might want to keep a food and exercise diary to see where the damage is being done. I think you should be able to include carbs in your evening meal, but you may have to restructure the rest of your exercise and diet to keep the weight off.