I need to cop myself on and be healthier but I’m struggling to eat healthily, any advice?

I’m 15 and have always had an awful diet. Up until about last year I refused to eat any fruits or vegetables, mashed potatoes would be as far as I’d go. I’m slowly beginning to introduce them to my diet but I’m still really unhealthy. I’ll now eat peas, carrot, parsnip, butternut squash, nutss and oranges. Thing is I find now for the first time, I’m beginning to gain weight and it’s starting to show, only a little bit but I want to get it under control and lose a bit of weight, however I’m struggling. I don’t know how, when I don’t eat healthy. I never eat breakfast (I know how bad it is but even the thought of eating in the morning makes me feel sick, I don’t know why) but I usually have healthy(ish) dinners most of the time. But besides that my diet consists of candy and processed food. I’m also really unfit. I don’t get home from school until 6:30pm everyday becuase I get extra tuition as I’ve exams this year and don’t have time to exercise then. I don’t play any sports and I don’t have much of a social life so I barely leave the house on weekends. Any tips or tricks to help me lose weight?