Very nice to meet you, Meegan! I relate to this. I'm a Xennial with mystery chronic pain which is most likely an autoimmune thing. I have some gut issues too. I also live with anxiety, depression, and OCD.
Nature, medicine, writing, resting, dietary limitations, counseling, support networks, epsom baths, trying to not get too cold have all helped me some.
My current doctor helped me a lot when she explained that medicine hasn't yet figured out all the autoimmune stuff. She believes me. She can tell when I'm flaring. She advised I get comfortable with the possibliity of never having a proper diagnosis.
Oh, and she does OCT, which is wonderful, but she hasn't been doing during the pandemic.