Nutrition help? :s

Hello, all.

I have my fitness needs supported but I am struggling with my diet. I could be wrong but my diet isn't so bad as in eating junk food and fast food - foods that aren't healthy. I still eat things like Nutella and Macaroni and Cheese so my diet isn't so great, either. I have gone up to my mom and asked her so many times about what to do with my diet and all she's given me was to eat more vegetables which I do love. Aside from eating vegetables and chicken, what else should I add and cut out from my diet? How can I get Omega three which is supposedly needed especially since I don't eat that much fish (a few times a year - lent)?

I also don't eat a lot of wheat anymore and now do eat whatever my mom packs me which could be a potato or salad or soup etc.

Also -sorry for asking a lot of questions-, how can I control how much I eat at a time? It seems that I am like never hungry but when I eat, I eat too much...