Help! Need advice on fixing my sensitive teeth

I need help fixing my teeth. When I was little I was very much neglected medically and physically, never showered, brushed my hair, brushed my teeth, was constantly near death because my diabetes gave me insane ketones all the time. Now, Growing up, it only got better. I'm fine now and can take care of myself and still being taken care of by my family. With this, my teeth started to rot. From the outside, my teeth look fine. Except I have two exposed nerves on both sides of my mouth on the top in the very back. They're both from cavities and they both hurt like hell. I'm close to getting that fixed but, the problem I need help with is that my teeth are so sensitive I can't eat or drink anything, especially anything sweet, spicy, or sour, without my teeth hurting. It hurts to a point where I begin crying. And it spreads to the rest of my head and it's frustrating. I can't put a band aid or something on it because it's literally my teeth. Now, that includes toothpaste. actually, ESPECIALLY toothpaste. I've tried every single toothpaste including at home remedies and ones especially made for sensitive teeth and it's so excruciatingly painful. what do I do?? It's so painful and a constant reminder of my childhood and I hate it so much. It's exhausting and frustrating and I'm so lost.