Hi there. So, there is a mental health disorder called PICA. That's what this sounds like. It's when you want to eat things that you should (dirt, ashes, paper, etc.). https://www.webmd.com/mental-health/mental-health-pica Copy and paste the article to read about symptoms and ways this is treated. I'm very sorry this is the situation. You should see your doctor right away and explain the situation. The first thing they will do is to do blood work and check to see if there is anything like anemia going on. They will also check to see if there are vitamin deficiencies either from replacing other food you would ordinarily eat with the cardboard or if there is some deficiency that is making you have the craving in general. They'll do an x ray of your intestines probably too. Just to make sure any health issues from consuming the cardboard are uncovered to keep you safe. Once that is done, then you can move onto the issue of PICA itself.
They actually often consider PICA an eating disorder and is often treated by a mental health care team. When they test for mineral or nutritional deficiencies, they then work to correct these if they are found. Correcting those deficiencies can actually overcome the entire issue so that's the very first thing they focus on. https://www.healthline.com/health/pica Since OCD is so often involved with PICA, that too is a lot of times treated along with. Because of that, sometimes they do use medication as well.
People overcome this and it is important to do so. Let me know what you think of this information.