Are you currently in Illinois, or trying to buy cannabis from Illinois and have it shipped to you?
If it’s the first option, medical cannabis has been legal in Illinois since 2013. You do need to have a physician certify that they are indeed your doctor and that you have a qualifying debilitating condition. You can read more here: https://norml.org/legal/item/illinois-medical-marijuana
If it’s the second option, and you want to buy cannabis from Illinois and have it shipped to another state, that is prohibited. Cannabis remains illegal at the federal level, so you cannot transport it across state lines.
Many CBD products are available anywhere in the US over the internet. Some global CBD companies have products available throughout the world. Evaluate the company for transparency, leadership, goals, full disclosure of contents with online lab analysis, and those that offer clinical support. These products do not contain any significant THC but I have found in most cases it has not been needed in common problems.