Portion control, first of all, and...

Just curious...have you had blood work done? There could be a health factor at work here.

I have weight problems due to underactive thyroid. They don't test for this on routine labs, only if they think you may have a problem (in my case, it was tested by my psychiatrist because I was having mood problems. It also explained the weight issues I was having).

If you don't have a medical issue, perhaps you should look at your portions. Watch the portions of bread, pasta, rice and white potato.
Let your largest portions be veggies. You can steam or roast them. You can use some olive oil and spices for flavor. Have some fresh fruit everyday.
It's great that you are a vegan but you still need to portion control.
Are you eating enough protein or mostly carbs? Try not to eat sugar.
For lunch I might have a mixture of fresh roasted or steamed brocoli, cauliflower, carrots and a small sweet potato and some beans. Very filling!! For snack I might have a banana with a tablespoon of peanut butter or a piece of fruit or even a handful of almonds or unsalted pistacheos.
If I have an awful craving for chocolate, I'll have a square of dark chocolate or a 110 calorie skinny cow fudge pop.
Just experiment and see what combination of foods is good for your body.

It may be worth keeping a food diary for a week - then looking at what you eat again.

You can become overweight even when eating healthy food...portion sizes are vital. Keep a food journal, keep track not only of what you are eating, but of how much.

A good place to look would be to the amount of starchy carbs you are eating. These tend to make it harder for people to lose weight.

In addition to everything everyone already said, as part of looking at what you eat, take a look at how much fat you are consuming - even healthy fat is still fat. And if you drink alcohol, take a look at that, too.