Can diet cause lightheadedness, dizziness, tiredness, and anxiety?

I've been eating poorly for literally all my life, I don't eat red meat and I don't eat that many vegetables or fruits. I know it looks bad, but I've become accustomed to it. Lately, I've been experiencing really bad lightheadedness and feeling faint. My eyes feel tired and droopy, but I start to get an anxiety attack as I feel this creep up on me. I had to excuse myself from my class the other day and go to the nurse. I'm 15 and a female (almost on my period, I think). I haven't had my period for about two months, though. I went to my doctor about this and she told me it could be because I don't have enough iron and nutrients. She's probably right, but I didn't do any blood tests (I did a blood test about six months ago, and everything was perfect). I just have this constant kind of dazed feeling and it's a real annoyance. It interferes with my daily life and I don't like it. My doctors appointment was about a week ago, and I've been trying to increase my iron intake. Nothing has changed, but I haven't shifted my diet that much. Do you guys have any recommendations for what I should do (maybe how I should start getting more iron intake or how I should change my lifestyle)? If you don't agree with the iron deficiency causing this horrible feeling, can you tell me what you think it could be? It would be so greatly appreciated if you could answer this, I've been struggling a lot lately. Thank you!