Validating My Pain: How to Cope When No One Believes You

How do you validate your own pain/experiences when the entire world feels like it’s against you? Since all of my conditions (asd, adhd, me/cfs, hEDs, fibro) have no tangible evidence of a condition/illness/etc. and are completely/mostly based off of what i feel, how am i supposed to know that it’s real, especially when it feels as if the entire world and the people around me are constantly invalidating it. I feel like what would really help would be having a community/friend group that can relate/empathise, but seeing as that hasn’t happened yet.. i’d love some advice on how to do it alone.