How to stop constipation

I only have a bowel movement once every 3 days, sometimes longer. I am nauseas A LOT, like everyday. I’m going to make a doctors appointment but I’m assuming it could be because I stay constipated. I honestly don’t eat the healthiest, I never eat fast food but I eat just frozen or processed stuff. What’s everyone eating to help them keep a healthy bowel movement schedule? I try to eat healthy but fruits & veggies get so boring.