How can I tell if I'm actually mentally ill? I have majority of the signs but I can't tell if I'm making it all up.

This is a completely normal and valid experience you have. You don't have to feel like you're making it up at all. It can be helpful to follow your gut and maybe speak to a therapist about your concerns. They can assist you in getting a diagnosis. This can give you a lot of clarity about the symptoms you are experiencing and it can let you know that your concerns are valid. Having an official diagnosis is also likely to make you feel like you weren't making anything up. Moreover, this can give you guidance on how to best take care of yourself in the future.