Strange eating habits?

Hi. I have some concerns that I want to share with hopefully some helpful people here.

I have only 2 meals a day, and I think I don't eat enough. My breakfast meal consists of a half a cup of a smoothie, a serving of fruit, and 3 walnut halves.

My lunch is a big meal, or so I think. I have a bowl of fattoush salad, a cup of Greek yogurt, and a small serving of whatever my mother cooks for lunch. Something weird I like to eat also is the white parts of a watermelon. I don't know if it's healthy, but I also have about 4 decent slices of watermelon rind and I munch on the white parts.

What I'm really concerned about is how I try to eat a bit of a lot of food in the kitchen. For instance, I eat a spoon ful of rice FROM the pot, then I eat a spoonful of some leftover dinner and so on. I do that while I am preparing my lunch. I think it's a self control issue.

On the side, I have been slowly and gradually gaining weight over the last month. I am not overweight. I also workout for at least 30 minutes 6 times a week. I'm 173 cm tall and 56 kg.

My period has been missed since a year or so.

Could I have some sort of binge eating disorder or a thyroid disorder? Why do I gain weight so easily? I feel like I eat below my range.