I control portion sizes by measuring, mostly, and also by eating more slowly (which can be hard to do with a baby needing attention) - it takes your stomach a good 20 minutes to realize you're eating, and tell you to stop. So if you gobble down a bunch in 3 minutes, it's going to still be saying "FEED ME NOW!!" but actually you've eaten plenty. Repeated large portions can also stretch your stomach out so it takes more food to fill it. By having smaller portions, your stomach will eventually get used to the smaller amount.
Also, you could try swapping in lower calorie foods. You didn't really talk about what you eat so I'm going to make some general suggestions.
If you are able to (and I know it's tough with a baby), tracking your food intake would be great. There are plenty of websites and smartphone apps (if you have a smartphone) for it, and it will give you a better idea of what you're actually taking in. I like MyFitnessPal because it lets me customize my intake goals. For example, I told it my goal is 70% calories from carbohydrates, 15% each fat/protein, more than the RDA of fiber, and 150% of my iron intake (since vegan iron sources are probably less bioavailable and I haven't been getting enough of it lately). So I can fiddle with it and use personalized goals. By doing that, you'll see if you even need to be cutting calories, and if you do, what you're eating the most of.
The exercise you're doing is great, but, as you obviously know, controlling what you eat is just as important (and probably more important). The suggestion to be careful with oil is a good one. You definitely need to make sure your getting healthy fats for your breastmilk, but oil is 100% fat, and it's really easy to overuse it. Avocado has more than just fat in it, so might be a better choice - just remember not to eat the whole thing at once if you're trying to cut down on your fat intake.
Other suggestions would be fruit as snacks, and higher calorie foods (rice, beans, potato, etc) paired with larger quantities of lower calorie foods (lettuce, veggies with little or no oil).
I don't have experience losing baby weight, so these are just general weight-loss suggestions. Your body might just not be ready to let go of the weight yet, I don't know. But I would definitely try fiddling with your intake and see if it makes a difference. Good luck!