My poor diet is worrying me

I (20f) am currently at college and am stressed about exams. I'm also dealing with a lot of stress at home due to unfortunate family circumstances. My ability to eat a balanced diet seems to have been majorly hit by my poor coping mechanisms. I've gone back to eating safe foods only. I'm eating lots of chicken nuggets chips and pizza. None of this is healthy. I am taking multivitamins but I know that's not a solution. How do I encourage myself to eat a wider diet of foods again?