difficulty with ruminating/catastrophizing

to start, i've had suspicions of having adhd for years but have not been able to seek diagnosis yet, so i'm undiagnosed and unmedicated. 

but in the last month or so i've developed terrible health related anxiety, and haven't been too sure of the cause of the sudden fear. i've been trying to find potential roots, from anxiety to trauma responses but i feel like those don't completely line up anymore either?? because lately i've been having consistent headaches that are likely caused by things not serious at all (sudden temperature drops in the weather, stress/anxiety, i might even need new glasses lmao), and i've even heard from others that they have been too, but the single second i had the slightest thought of "what if it's my brain" i haven't been able to stop thinking about it and catastrophizing constantly. the headaches have even started to let up in the last couple days, mostly just being a little uncomfortable, but i can't let the thought go. up until the last couple days i hadn't even considered my potential adhd as part of the issue until it suddenly clicked for me. i'm still not sure if this is the key but i feel like acknowledging it may be able to help me. i just don't know how to break the chain of thought