Other picky eaters, how do you get the nutrients and vitamins you need?

I’ve been a picky eater since I was a kid, i’m hyper sensitive to smells, tastes, and textures. I really only like more milder/bland stuff and have a diet that’s mainly just like chicken, potatoes, and pizza. I want to be able to get everything my body needs so i’m not slowly killing myself but I hate having to eat new things. Is it helpful to buy supplements? What all do I really need to be “healthy”?